Well the results are in. I got 2 sets of bulbs for £6. One was a 20V H10W and the other was a T4 something or other that had the same base and made crazy claims about white light and super brightness with xenon technology.
The H10W 20V seemed a bit brighter than standard but still very yellow. The T4 whats it was ultra shite.
Looks like i'll be stumping up for some LED's