Thanks for the reply. I checked the policy documents, and an increase in the declared mileage is not on the list of disclosures, but there may be a loophole in that it states a change in use of the vehicle must be declared. That would normally be only if you used the vehicle for business use, racing, commuting and such like.
Not only will they be increasing my premium with an ex gratia payment, they will also charge me an extra £35 admin fee for changing the policy!
My point is also that if you had declared say 4,000 miles p.a., and you actually did 4,001 miles, and then had an accident, your policy would be null and void because you had exceeded the declared mileage!
Surely this can't be right?