Hmmm, not really sure what is happening here. Are you saying that Elephant is trying to charge you more for your old policy on the basis of non-material declaration or is this a new quote?
If it's a new quote then walk away, I don't see the problem here. If it is Elephant trying to charge you more for the policy that is about to expire, then you may have an issue which will take a better 'insurance' head than mine to resolve.
Legally, you MUST declare any and all convictions within a set period (usually five years) at the start of any policy. If you do not or you 'forget' then you are in breach of contract and could have insurance denied, a policy cancelled or restrictions. You must also notify an insurer DURING a policy of any conviction so really you have very little excuse. SP30 is not exactly the activity of a hardened criminal but you should have declared it and this is where they could feel that you have deliberately 'hidden' the facts from them. Tread carefully - this could cause you problems - more from fall-out than anything else.
SHARK!