Small congregations, and anyway it ain't just the Anglicans.
Many, many religious and charitable organisations use these facilities, so you may think the Anglican's are not deserving, that's up to you. It also isn't about cheap Chinese microphones either, you still have to have a receiver(s) and PA system on the other end, which also come int to the equation. We use mics because we have deaf people (not all age related) in our congregation, and we also include as many people as we can in the service, not just those with loud voices.
So Ofcom, it isn't just the Anglicans, its all Christian, Jewish, Muslim, Hindu, etc. places of worship, plus youth clubs (usually less well off than churches), amateur sports clubs and so on.
As to slavery funds sloshing around in Anglican coffers, don't be silly, that went years ago, very few established churches have deep pockets, even in well attended parishes, a percentage of Christian church money goes to good deeds anyway, so I suspect any restitution has been paid back to the communities affected in the form of Hospitals, Schools and Social Services, there is a finite amount of money available to any organisation, if you pay restitution with one hand, then you take away aid with the other, or hadn't you figured that one out.