I have called them actually and they said because they are temporary and just tyres i didnt need to inform them!
As for grip, its awesome. I have 2 like new tyres on the front not balds. Where as before i had about 2mm tread left on the rears. All these posts are funny, so far youve not been right about anything. Thats a sign to shut up :D
You're failing to understand anything that's being said. Just for the record it's the rubber compound that's different, and having full tread on summer or 'all season' tyres on the front doesn't alter the fact that you have a potential mismatch of grip front to rear. If you are driving around slowly in periods of low temperatures then I'm sure you'll get away with it, but it is a risk. I have a full set of winter tyres on my IS200 Sport as for the sake of spending a few quid on a couple of tyres it just isn't worth the risk, but I guess that your location probably hints to why you decided otherwise, although I would have thought the risk higher in Scotland due to the increased chance of low temperatures.
Presumably you have just changed the tyres on two of your original rims?