Adrian Sims wrote:

Do you mean the luxeon ones? If so just how bright are they? Are they
actually GBP12 per LED?!

Luxeon Lumileds are astonishingly bright - to the extent that when
working on optics based with them I have to wear gas welding goggles to
stop hurting my eyes. They knock any other LED into a cocked hat for
intensity

And they are expensive.

Steve