Andy,

Shark is right here. You must declare any and all convictions within a set period at the inception, throughout the life and at the renewal of the policy.

Elephant are well within their rights to charge you any additional premiums that they require based on the new risk you have presented to them. Nearly £500 is not ridiculous at all; if you had mentioned this to the insurer and they came back with the quote, then you would have taken the policy out elsewhere - saving yourself a few pounds in the long run!  It is just unfortunate for you that the risk you supply coupled with the SP30 amounts to such a high AP with your current insurer; as you can see, every insurer is different, and Halifax do not seem to load for the SP30.

This money is owed to the insurer and they will want it. However, another forum member had a similar enquiry and he posted back (within this week) that he managed to come to some sort of 'compromise' with his insurer. See if you can do the same.