Forgot to mention in my OP. A few months ago i hit a curb in a petrol station and burst my passenger front tyre (yeah i know, twattish thing to do lol) and since putting my spare wheel on the problem has been much worse (it was doing it a little bit before the bump). Could the bump have made the original problem worse or could it be the different wheel and tyre that are highlighting the problem.

Phil - all tyres are in good order, correct pressures (usually put about 32 p.s.i. in them) and are mid range Toyo tyres.

Thanks for replies so far guys.