You may think you are safe with your Travel Insurance but be aware, the first get out clause is alcohol! Oh yes they dont cover you if you have had a little drink! Or left your cash in a taxi........
Anyway you Brits make sure you get one, costs nowt if you do it via NHS website, you just need your NI number, that stands for National Insurance but unlike most insurance policies you dont even need to pay anything in, entry is free at Heathrow.......