I'd be less worried about the poke and more about the stretch. Rozzers had my pants down with regards to the stretch tyres I HAD on my mk2. (Yes coppers are eager round my way). Tyre manufacturers set out recommendations with tyres and the correct fitting. If there not within these recommendations then they can be deamed unfit for purpose, hence ending up with your prized posession in the pound. Also, you should inform your insurance company, although the chances are they'll promptly tell you they won't insure you with stretch tyres on!!... But if for some strange reason they do, at least your covered if the worst shud happen. If you don't your insurance will be VOID for not declaring the stretch tyres (it is a modification) and then the coppers will well and truly shaft you!! (It's the voice of experience this!) But there again on the other hand, you could drive around for donkey years and not have any problems at all, it's just the risk you take!!
There is no law with regards to having stretch tyres, there not illegal, but you can still get shafted for them!