Well, I now have Vista installed after swapping computers. Something catastrophic happened with my own computer's motherboard whilst installing Vista. After a day trying to get the computer to play ball a new BIOS was installed and Vista could also work properly on that computer.
So - a word of warning for installing Vista - upgrade your BIOS beforehand. I have no idea why the BIOS is incompatible as the computer is only 18 months old, but at least it now works, and I hope this post stops people heading down the same blind alley.
The boot process is definitely taking much longer than Windows XP. Installing most software is also mostly successful. The ubiquitous TortoiseSVN works seamlessly.