Well, it's not that there are fewerplaces, it's the Protestant Reformation! Catholic churches have them; Protestant, even Anglican, don't. Even Thomas Becket's remains were tried for treason by Henry VIII, hanged (again) or burned (I can't remember which) and tossed in the Stour (the creek at Canterbury).
Protestant England is not a place where relics are kept in (Protestant) churches, not since the 1540s. That was my point. Mom might have been to see the relic, since every Catholic church has to have one, usually in the altar stone, but Harry's Muggle England is not a place where they are much in evidence.

I love relics. A friend had a small collection. Even one of St Severian.