You can actually self register for VAT before reaching the threshold. If you pick up publications;
Notice 700/12
Notice 700/21
Notice 700/1
Notice 700/15
Form VAT1
Notice 700
These will give you the details of becoming VAT registered and what its all about. You can request these from 0845 010 9000.
P.S The threshold is now £54,000
Regards
Homer