Cheers Viney.
So I still need to know what length chain I will need if I fit a 46 to the rear and keep the front standard.

I do, do a lot of A road riding but I prefer to ride in 5th rather than 6th to keep the rpm slightly higher and give me more grunt! So thats why I was thinking if I increase to a 46 I will have more acceleration in lower speeds and will be able to put it in 6th to tame the extra rpm?! Make sense?!!
Cheers