As you know, the back street bodgers that 'fixed' your puncture on the wheel don't actually know what is recommended under British Standards and simple 'best practice'.
Tyres with a very high speed rating are not rated as suitable for repair, so the places that would not fix them are correct, the back street place does not care, and will probably change hands often, big places are more careful about sticking to the recommended actions, they have much more to lose.