Betfair may be a desirable gambling platform to play on for you but if your region is restricted then you should forget about it and move on to reputable gambling sites without restriction, if you use a VPN you will still run into trouble in the long run. It's better to stay away than risking your account and funds by bypassing restrictions with the help of a VPN.
At least, he can ask the support system if their site allows using VPN and will not have a problem cash out the win money if he wins. By doing that, he can get the right answer from them to decide whether to use VPN or search for other reputable gambling sites. But move on to the other gambling site that does not require too many things will be better if he does not have any problems in the future. Many gambling sites are out there or from this forum so he does not have to feel difficult to search for the right site.