The VPN I use https://www.privateinternetaccess.com/
, and have used for years, is tested and working fine with both iPlayer and C4/All4 as of this afternoon. Current progs are playing without any problem.
It has multiple servers worldwide, including 2 in the UK (London & Southampton), so when the BBC is playing "whack a mole" and takes out one IP address, the second location offers an alternative without changing VPN provider. They are also pretty prompt at putting up clean IP addresses once a BBC ban takes place. (Existing London & Southampton IP addresses are currently both clean for BBC and C4).
I'm sufficiently happy with them that I now just sign up for a year and take the discount, but try them out over a month and see how you get on.