I think that the regulations and rules that were set in place by many governments are not sufficient enough to prevent gamblers from making drastic actions in their lives, especially to those facing severe depression, anxiety and addiction in gambling and other things related to it. Mental health I think should also be considered as a big loss would definitely affect their capability to interact in the real world. Make laws that would only allow gamblers with a strong mental faculty and just allow those who don't to only play lottery and small town legal gambling that only needs very small bets.
This may not be sufficient but this might help, complying with the requirement to prove that you can handle your loss or to gamble further after reaching the 100£ cap will limit gambling addicts, especially those who are in the lower-income households. Anyway, the government can always change the rules or prohibition depending on the circumstances or what can be beneficial for both the government to collect taxes and to limit gambling addiction.