Try Leightons in Birmingham. They did my passenger seat in yellow /white to match the numberboards & it only cost me £20. Great job too. they used the existing yellow for the middle as they hadnt got a yellow that matched. Very pleased.
I did have- I will get it next time I'm passing as I work in Brum. Can't say whether that price is valid for anyone as we use them for covering our Fork Lift Truck seats, so he might have done me a special cash deal!