Never knew this was the case, i.e. not permitted if close to an edge, its new to me, when I had similar punctures close to edge, but not on the edge, a local tyre fitter promptly repaired it without referring to any legal issues with regards to permitted repairs, though I thought it was more to do with technical issues such as not enough depth or material and I know about side walls cannot be repaired.
Thanks for this information, you are rest assured it will be stored in my head from now on.