Just to add another quote for a company for Paul.
I'm with
CIS (co-operative insurance) and they do not allow any modifications other than standard parts-this means that wheels must be the same size as what they were when the car left the factory (Citroen 13" alloys are allowed however) however interior (seats, ICE, etc.) you do not need to declare.. at least this is what Martin the CIS telephone advisor person told me. "So a 106/vtr interior is considerred standard as peugeot and citreon are both part of the PSA group"
Tbh CIS aren't worth getting insured with if you intend on modifying. Parts for my car are laying around the house e.g. strut brace, and my induction kit was, had to sell it.