I don't know your local laws in the UK, however, I'll just pass on something that maybe worth looking in to.
In these parts, you can notify the Insurers of just about any modification and it will just be a notation on the paperwork. They'll happily take your money and you think you are insured, however if later when making a claim, they find the modification non-compliant (or put another way, illegal) they will knock back the claim as they say it's up to the owner to ensure that the vehicle is legal when being driven.