In some craft stores here in the US, they sell LED strips that are very thin and narrow. I'm certain you would have no problem sourcing them in the UK. They would probably fit under the keys between each row with no problem, but the biggest problem is trying to hide the power source and switch to turn them on and off. I know on my AL PowerBook, the keys are painted silver, and have transparent letters which could easily be lit up. I think the bigger Aluminum PowerBooks (15 and 17 inch ones) came with a lite up keyboard.