I ended up sending back the Samsung SSD, and bought an Mtron MOBI 3500 instead. (After a bit more research I found out that the Samsung was somewhat better, but never mind it was too late by then). Installed Windows Vista on it etc., it did what I wanted.
Today I installed the Windows Feature Pack for Storage 1.0 update and restarted my computer.
I was greeted by the lovely message:
DISK BOOT FAILURE, INSERT SYSTEM DISK AND PRESS ENTER.WTF sprang to mind. I really wanted to blame the update I just installed, but this is at BIOS level so I will have to put it down to a coincidence.
I restarted, checked everything was set-up/recognised OK in CMOS setup and tried again. This time it booted like normal. Clearly I will have to keep an eye on this...