i've currently got the lurcher insured with the NFU, it costs about 7 quid a month, and it covers him for 2 grands worth of treatment per accident/injury. i'm going to get the terrier insured with sainsbury's, and switch the lurcher to them when his policy is due for renewal. my cousin is a veterinary nurse and says that sainsbury's are good, not too pricey (about 12 quid a month, they cover up to 6,500 per illness/injury for that, and lifelong treatment as well), and they almost always pay up with no problems.
don't mention it's a working dog, and say it's a mongrel. also, my cousins top tip