The 25 % is off everything on the site (Mens and Women's), a few of the cheapest examples I can find are:
£50 and £60 shirts now 11.25 + cashback = 10.35
£400 suits now £105 + cashback = £96.60
£25 Cufflinks now £9.37 + cashback = £8.62
The discount is taken off at the checkout, just before you pay
End midnight Sunday 23rd November 2008.