From what I have read a car is not illegal without a cat as long as it would pass an emissions test.
I can't fit the exhaust until next month as my current insurer won't cover any more mods as I already have stage 1, panel filter and uprated discs. When I asked them to add the exhaust they knew it was a full stainless from front to back and only asked about the power gain, then they noticed I already had the above mods and told me that they couldn't cover me.
I'm not losing a years no claims for the sake of a month and an exhaust, just narrows down my choice of insurer for my next policy
Adam
Cheers I'll be in touch at some point about the reducer ( hopefully I remember well before the MOT is due)