I'm with NFU and pay £362 annually for my two, so about £15 per month per dog. They have lifetime cover of up to £4,000 per year with a £50 excess.
They were excellent last year when I paid out nearly £2,000 relating to William's back problem, including lots of physio sessions as well as the MRI scan and more routine consultations. Hopefully William won't have any further back problems, but if he does they'll continue to pay out for the same condition up to £4K every year.
Tracey, is your lifetime cover different? Unless I've misunderstood your post, it sounds like Tesco pay up to £4,000 for one condition during the whole lifetime, not in each insurance year?
Hopefully this has been a one off for poor Jasper.