Thanks, Both.
Yup, aware of the SSD disadvantages, but in this case - as a dedicated boot disk - the advantages are attractive and the disadvantages somewhat mitigated so I will dip my toe in the water and see what happens. After reading your advice, M-B, I have decided on a Crucial M4 2.5" 64GB SSD which at eighty quid is not "cheap" (in the throwing money away sense) but won't completely break the bank if it all goes Pete Tong.
As a step to reducing the amount of writing done to the disk, before I start using it in earnest I might have a go at moving "Documents and Settings" to one of the physical HDDs.