Other than using iPlayer, another use for me is to access the Internet while I travel to China.
From what are suggested here, and from Internet reviews, I think the big and good ones are: Nordvpn, Express vpn, and PIA. Mullvad seems to be excellent too, but I think it is a smaller company. Nordvpn was hacked awhile ago. and PIA will soon be acquired by Kape Technology.
If Nordvpn has not been hacked, it seems to be a clear choice. There are many happy customers too.
Maybe it comes down to Express vpn vs Mullvad.