would fitting the 2 tyres to the rear of the car (driving wheels) be ok in the short term to give me extra grip climbing snowy hills etc?
Derek,
I would wait. Every manufacturer and motoring organisation says don't mix them, and for good reason.
- Acceleration - will be good.
- Cornering - lots of understeer, which is OK if you are prepared to deal with it, by going at the speed you would have gone at if you still had 4 summer tyres.
- Braking - every braking action will be a handbrake turn (in effect). The rear wheels will do lots of braking, the front next to none. Not good at all, and quite possibly worse than if you had 4 summer tyres!