Here is a bit of advice from personal experience for anyone buying travel insurance.
Make sure you buy it from a big reputable insurer as trying the save the pennies would be the worst thing you can do here.
My mum made the mistake of taking out cheap travel insurance with Avanti insurance and now she is in deep crap as she has taken ill on holiday and they are dragging their feet to validate her claim and provide care under the insurance policy.
They need all sorts of paperwork before they can provide assistance. Don't try to buy the cheapest travel insurance you can as it can cost you your life. £50 saved on a travel insurance policy is not enough to sacrifice your life for.
Always look at who the underwriter to the policy is from the small print as they are the ones responsible for paying the large medical bills. Make sure they are a well known insurer if possible but as a minimum that they are a UK insurer as UK insurers are subject to more stringent standards.
Definately avoid any insurer whose underwriter is Mapfre who were the underwriter to Avanti insurance.