Well I have a date for my SVA test. 21st of April - it was the last date that the Leighton Buzzard centre is doing tests (apparently). They were very helpful though - phoned me up to discuss the date and time rather than just allocating one.
They wouldn't give me their direct phone number though (just in case of - err - last minute problems) - you have to go via the VOSA call centre. 1471 comes in handy sometimes..
Robin