Judging by the number of nuisance callers it is reporting as having
blocked, the number of such callers trying to get through has
increased, just as I put the new phones in.

Mostly their number is 'unavailable, some present a number with 0020 or
00??. Sometimes the 0020's are valid numbers if the initial zero is
deleted. I am getting calls from spoofed local numbers, usually none
existent numbers, over the weekend one was spoofed to present a very
local number from within the village, so I rang the number just to make
sure - there had been no one in the house at the time, to dial us.