You have to spend over £20 for the £20 voucher(so you get it free)
and over £25 for the 25 voucher (so you just pay for delivery)
most of the stuff on the site is shite but they have got some tidy stuff there.
Iv ordered with them (pack of 3 boxers and a tool kit comes to £30
use the £25 Voucher and hey presto I payed just over £5.
BTW, if your not happy returning is FREE if you use the local courier they recommend. They'll even come and collect it.