I've used 'TMSM Travel Insurance from Club Direct' online for a number of years (usually single trip - up to 30 days worldwide). I have never had to make a claim (fortunately), so I can't vouch for their side of the bargain. They do however offer very similar cover for a lot less than many other online brokers.
I claimed for a camera (which I dropped at the airport in a bag on whilst returning to the UK), from Tesco. They were excellent, speedy and efficient. They offered new-for-old and the initial offer was a little low (it was an old fully manual SLR camera so difficult to cross reference to todays cameras) and I submitted some information on its features and they lifted the offer without question.