Ok quick post...

I run 215/40/17s...all round.
Have just bought new fronts but 215/45/17s...

Will these be ok to fit and how will it affect the car!? Need to know before I fit them otherwise I will have to send them back and start again in my tyre search

I run 215/45/17 all round with no apparent issues.

It won't make a big difference but your gearing will be higher so your acceleration will be slightly blunted.

I suggest you put the larger tyres on the back and the 40 profile tyres on the front to stop this.

The difference is small however.

I take it your car is not lowered. On mine with Bilsteins B6 and Eibach -35mm drop it catches the arch (the front plastic bit on full lock). The ride is nicer 17" alloys with 45 profile tyres than 40.

Yeah. It's not lowered. Agree that it's a nicer ride.

what is the optimum pressure on 45 profile?