That's good to know, thanks for the reply's. I wasn't 100% on the 255 but that's now cleared up

. I'm running 265/70/16, with a lift & a lot of front wheel well trimming. Can't go full lock without rubbing on the swaybar but that's OK as it's only about a 1/4 of a turn that's been lost in the steering.
My insurance provider tried to tell me my tyres were not allowed on my KJ but after checking with the local RTA (Roads & Traffic Authority) I think I'm fine. As long as the load ratings are equal or grater than the stock tyre it's OK, also can't be over 15mm taller so that's cool (I'm taking it means 15mm each way). + the rubber must be suited to the rim width. The 265/70/16 Cooper STT can be fitted to a 7" wide rim & up to a 9" I think.
The reason for the question was that I was 1st told it could be no wider than 15mm of the original factory tyre & if so it was not legal (not so, RTA) So I say I'm OK but need to get new rims later as running wheel spacers isn't legal here. 5mm helps but a 13mm offset will do the job.