Had this issue with my 1st 225 - Didn't mention it to my insurance company - who would? cheap insurance But when I had my little accident!! My world nearly crashed around my feet as the insurance company weren't going to payout. If you read the small print it states that you need to highlight if the details aren't right. Moral of the story it cost me an additional £96 pound to ammend my policy but it could have cost me a whole lot more!!!!
I had this same problem, it's a shame the old threads had been lost.
The V5 said nothing but "Renault". I'd told the insurers (Tesco) the car was a 225 anyway, but they couldn't find the 225 on their lists and all the docs came back as a Dynamique. They said this was fine (and I asked them several times) because I'd given them all the information I could.
This years policy does now state "RENAULTSPORT MEGANE 225", but the V5 did not.
TO amend your V5, just cross out whatever it says and write "RENAULTSPORT MEGANE 225" underneath in pen, sign the box at bottom and send it to the DVLA. They'll send you out a correct version a few weeks later.