Thanks Nick
I called bmi Diamond Club, who liaised with their Virgin counterparts and called me back. It appears that there is availability on the outward leg (3 July 2004) but the return leg (23 July) cannot be checked yet as seats have not been released as yet.
They suggest that I call again early September. As I'm getting the feeling that Virgin seats for miles redemptions are released at the same time they release flights for normal bookings (336 days?) I think I might just get on to them a bit earlier....just to be on the safe side.
Alex