Hi Mary,
we decided to insure with Marks & Spencer. Boysie is also a 'rescue' dog, so we didn't know too much about his history. We liked the fact that there were were annual limits (6,000), not per condition limits, as a relative of ours had just discovered that their springer was no longer covered for his arthritis. It also covers other benefits such as 3rd party liability (2,000,000),and complimentary treatments up to 250 (useful when he had his hydrotherapy), and will provide lifetime cover. You can further reduce premiums by incresing your excess on the policy.It cost us £165 this year (including a discount for paying with our M&S card), and what with his leg problems this year we have more than got that back already! (They also have good house insurance too!)
Hope this helps
Maria