Hi Chris,
I wouldnt bother with 6.5 - 7.0 and 2000 are significantly different (not just more + better features but also i believe under the hood), and i get the impression that although there are a number of places that still use 6.5, it's being phased out in favour of 7.0/2000
What i would do, presuming you're learning from home, is get a book with an evaluation copy of SQL Server2000 (there's a few about - MS Press Inside SQL SErver 2000 and SAMS SQL Server 2000 Unleashed spring to mind - the second i found v. useful for learning). They cost nearer £40, so you'd even be saving a tenner to go to the pub with...
Just my 2 cents (or rather 2 pence), others might disagree
HTH