Wifes corsa had a slow puncture a couple of weeks ago I kept checking it / pumping it up every couple of days and middle of last week used some of that puncture repair foam, but it didn't help, ended up swapping over to the spare and took the flat to nearest Kwik Fit place only to be told if its had that puncture repair foam used in it then it can't be repaired, has anybody else come across this or do they know if its true ? or was he just at it to get the sale of a new tyre ? ( which he didn't as I'll look around first for a better price that what he was quoting ).

Yup its true, once the foam is squirted inside the tyre is usally scrap. You cant get the plugs to stick inside and seal once the foam has got in there.

I have been told the same by my local independent tyre dealer.