All you need to do to claim £5 free from Prezzybox, is follow the link and 'like' quidco to receive a code for £5, FREE...
There are quite a few cheap things to be had, but they have been a little sneaky and reduced some things by a few pence to save having to give them away with a 'not available on sale items' clause. P&P of £3.95 is payable however - not sure if the code can deduct from this or not.
Here a few examples of things that you can grab for 'free' with the code:
This offer's valid from 21st to 27th February 2011. No minimum spend required. You must redeem the voucher by the 6th of March 2011. Cashback is not compatible with the £5 voucher and cashback will be declined if the £5 voucher is used. The voucher is not valid on sale items.