I'd buy:
Samsung 500GB SSD 840 EVO SATA 6Gb/s Basic - £209.99
+ Western Digital Caviar Green 2TB SATA 6Gb/s 64MB Cache - OEM - £65.99
Use the Green as an archive/backup/storage drive and go nuts with the SSD as main drive.
You can save £30 by getting a Crucial SSD same size
You can save £20 by getting a 1TB HD
I see, how do backup a constantly changing drive though? surely its too much of a pain.