E111 (card now, not form) entitles you to 70% of medical costs. So top up with travel insurance. Trailfinders are quick and easy but no doubt their are others.
70% of medical costs!, That is just the immediate operation, it will not cover you for the nights you spend in hospital, or possibly having to be brought back to the UK.
Typically travel insurance can be bought online for around £10 for the week. It will also cover you if the pickies have more than expect of you site.