It's a paradox frequently noted by visitors to churches that the number and size of 'Welcome' signs displayed outside is in inverse proportion to your chances of getting inside.
Milton, Cambs, is an example. A majority of the other churches in the area north of Cambridge are in my experience generally open, but Milton has always been locked on the occasions I've tried the door. (There's no information available about keyholders.) This despite there being at least two 'Welcome' signs, one of them big, colourful and prominent. If you're naive, simple and trusting like me you obviously assume that this means that you're welcome to go in at any reasonable hour, perhaps to pray, reflect, have some quiet time or (as in my case) for mostly aesthetic and historical reasons. However, that's not what 'welcome' means in this context. I don't doubt that you would be very warmly welcomed if you attended a service, but you're clearly not welcome at all to go in at other times.
Peering through a south aisle window reveals a partial explanation for this. The aisle is full of expensive-looking musical equipment: amplifiers, music and microphone stands, perhaps a drum kit. If they belonged to me I certainly wouldn't want them damaged or stolen, so I'd want them locked safely away when not in use. (It's a shame that they're not simply locked in the adjacent parish rooms, or a large cupboard, though.)
The presence of the musical paraphernalia hints at another reason why the church is hard to get into: the congregation presumably prefers an Evangelical (or what is sometimes called 'Low') style of worship, otherwise known as, rather demeaningly, 'happy clappy' (though I'm all in favour of happiness, and can't see anything inherently wrong in clapping). A certain proportion of churches of all shades of Anglicanism are generally kept locked, but I think it is an empirically verifiable fact that this proportion is much higher than average if the church's congregation is Evangelical.
Why should this be? Partly it's the expensive, desirable, easily stolen electronics etc usually used by such worshippers, but, more importantly, I think it's the attitude to the buildings. I realise I'm making sweeping generalisations here, but Evangelicals tend not to be much interested in the history of their buildings, which are seen simply as utilitarian spaces. (The document linked below refers to All Saints, Milton, as 'the existing church plant', which is very revealing.) Some of them even seem to think that taking an interest in the church as an historical artefact or as a thing of beauty is verging on idolatry. The one thing that matters is the Word; everything else pales in comparison. They don't relish their buildings' histories, and don't really understand why anyone else does. Thus they keep them locked.
A pertinent case study is that of Stamford, Lincs, which has five medieval churches. Four of them - Sts John the Baptist, Mary, Martin and All Saints - are in my experience generally open. Some of them have discreet sandwich boards outside alerting passers by to the accessibility and welcoming nature of the churches (which are I assume taken inside when the church is closed). The fifth, St George's, is Evangelical and has permanent enthusiastic day-glo banners outside (or did the last time I was there) shouting their pious inhospitality, and is - why am I not surprised? - always (outside services) locked.*
Naturally, how people choose to worship is none of my business. Evangelical congregations can clap as happily as they like as far as I'm concerned, and if they keep the roofs of their churches from leaking then that's a big plus for me in this age of dwindling congregations and concerns about how we're going to maintain our architectural heritage. Maybe having some churches locked for a while - after all, eventually attitudes will change, new congregations will arrive, and they'll be open again in a decade or two - is a price worth paying for the preservation of the buildings for the future. I'd still very much prefer to be able to see inside them now, however.
Fashions in styles of worship have changed several times over the centuries; a process of moving and removing furnishings and fittings has been a feature of churches everywhere for as long as they've existed. Evangelicals, I think it's fair to say, are very keen to maintain and even accelerate this tradition. This sometimes brings them into conflict with more conservative Christians, and with anyone who doesn't want churches to be pretty radically altered. Returning to All Saints, Milton, where we started, here's a plan of the recent reordering and extension:
(This is from the website of David Joy Architect (see here).) The extension to the north roughly doubles the floor area of the medieval church (and makes it very much more suitable for 21st century visitors). The most obvious changes to the church itself are the removal of the pews (which were presumably Victorian), and the sidelining of the chancel, traditionally the focus of worship in a church. The altar (or communion table) has been moved from the east end to under the south arcade.
Traditionalists will be outraged by this. See here, for example, which fulminates about the church being 'nearly wrecked by simplistic happy-clappies'. Me, I'm not so fussed, with the major proviso that these alterations must be reversible. Some people object loudly when pews are thrown out and replaced by chairs; it's true that sometimes the chairs are ill-chosen but otherwise I think this is usually a good move. Pews are dark, bulky, cluttering and are very hard to move; chairs create a feeling of space and are easier to move, so the nave and aisles can be used for a wide range of activities. The country is not short of pitch pine Victorian pews, so their ejection is no great historic loss. And if people want their altar in the nave, then I'm very happy for them to put it there. As I've said, in a few decades it can be put back in the chancel if that's what future congregations want.
As long as the alterations haven't involved the destruction or removal of any features of historical or aesthetic significance I can't work up any outrage against them. But, to go back to where I started, I do object to churches, built and paid for by the whole community to be used by the whole community in perpetuity, being permanently locked, especially when salt is rubbed in the wound by garish hypocritical 'Welcome' posters defacing the exterior.
* To be fair, I'm told that by calling at the church office (a quarter of a mile away) an accompanied visit can sometimes be arranged. However, to the best of my knowledge this is not advertised either on the church website or any noticeboard. In any case, accompanied visits are rarely satisfactory; the accompanist usually gets bored and, intentionally or not, makes the visitor feel rushed.