Simple question: in the UK, where can I find 2x5.25" drive cages into which I can put 3 IDE drives? I don't need hot-swap.

When I looked recently, I found a couple of websites that sold these in the US, but they wouldn't ship to the UK in quantities less than 4 or 5.

The questions not so urgent now I've decided to put one of the 250Gb disks in my new Windows box (when it turns up), but I remain interested.

Three? As in three 3.5" into the space of two 5.25" drives?

You could try a visit to your local hardware store and buy some aluminum sheet. Chop and drill till you have a pair of side plates that join three drives. Mount the bottom most as normal.

Yeah, I'm with gbeer on this one... It's all about the hack. All that matters is that the drives fit reasonably well into the allotted space, have some airflow, and don't wiggle around. Screws 'n holes, man...