Thanks for the tip. knownhost do indeed seem like pretty much what I was after.

I've just been through the process of emailing westhost.com about what exactly their VPS system gives me. After a first round of assuring me that I had full control of the virtual machine, and could install whatever software I wanted, it eventually turned out that ports under 1024 are "restricted", and that certain directories "are off-limits as they contain system commands". In other words, I don't have full control at all, and I can't install whatever software I want. Boo, hiss!

So I'll have a go at emailing knownhost.com to see what they really offer me. At three times the price of westhost, I'm expecting something a lot better.