I always thought the same as you and a tyre couldn't be repaired if it was near the edge
Depending on the exact damage and the area sometimes it can be safely repaired. Take it into a specialist tyre
shop, not kwik fit or the like
They might be able to
help you if they consider it is safe to repair
There are certain tyre places that claim to be able to repair tyres that have punctures outside the area where a repair is normally permitted. Never used one but from what I have read on other sites they charge a large sum and your tyre can be away for several days. If you have a car like the Leon with no spare that is not really an option.
But think about it, your tyres are the only thing between your car and the road. they lead a very hard life and its a miracle they last as long as they do. Personally I would never be happy driving a car on a tyre that had been damaged on the shoulder or sidewall, if it lets go the consequences are going to be potentially serious.
Forget the dealers kind offer of 10% off, go to a local independent tyre dealer and you will get a matching tyre for much less than that and hopefully many 1000's of miles of worry free motoring.
As for Blackcircles, a chap at work used them a few months ago, saved a large sum of money but the "recommended" garage they sent the tyres to for fitting mullered his alloys using ancient fitting kit. Blackcircles not interested, fitter points to notice on the wall which says they have no liability for damage to alloys.