I also use Insure and Go, Annual policy as we go abroad about 8 weeks a year. Black policy their top cover cost about £140 for all family but they start a lot cheaper, think they have 5 levels of cover.
Don't go with cheapest, I did with Asda 2 years ago, they were terrible, gave up on the claim in the end, I understand they have changed their under insurers since.
Can't say what a claim is like with I&Go but their cover looked very good for the money.