I am sure they all could block VPNs if they want by just measuring the PING time, but I can't see why they would want to.
This geoblocking is crap. They say it's to protect content, but I think it's to do with adds.
If I look at the same overseas site and same program on both 3BB fibre internet connection, and True smartphone connection, at the same time, the program content is the same but the adds are different.
So if the host site has lots of different feeds, they have lots of different adds = lots more money.
I reckon a way to get around blocking of VPN IPs would be to have a say Microsoft Server set up at your relations place and VPN to that server.