I did a search on the internet and came up with a site that offered advise: A number of providers offer policies that give higher levels of cancellation cover:
Thomson, in partnership with AXA, offer cancellation cover up to £20,000 (online policies only)
American Express (Tel: 0800 028 7573) offer cancellation cover up to £12,500 pp.
Post Office (Tel: 0330 123 3690) offer cancellation cover up to £10,000 pp.
Insure and Go (Tel: 0330 400 1383) offer cancellation cover up to £10,000 pp.