I used to have my dogs insured but the premiums kept going up, as did the excess, so it wasn't piece of mind to have the insurance, just very expensive.
Thankfully my dogs aren't particularly sickly or accident prone, so in the last couple of years, apart from routine vaccinations I've been once with each dog.
For those on benefits, you can get free vet care through PDSA even if they don't have a clinic in your area. Just thought it might be useful whilst on the subject of cost.
http://www.pdsa.org.uk/eligibility.html