we still have "just" a reasonable anti-sub capability this is what the type 23 was designed to do
13 type 23s. Assuming three in refit or repair, one in port for turnaround, ignoring international obligations, that's nine, so that's 855 miles of British coastline each. Can't see them being very effective when they're that thinly spread. And that's inshore, before considering the full extent of waters we might want to use them in.