Thought I'd just pop back in and say the eBay bulbs from PartsULike worked great. I ordered 2 packs ( 8 bulbs ) which came to just under £7 and was enough to do interior front and rear lights and also the number plate lights.
Really happy with the difference, the bright white look is so much smarter than the previous yellow bulbs.
I'd also like to get the door/puddle lights, and boot light changed to brighter LED's too - are these the same bulbs? Or are they different?