As per the linked advert, you can get 20% off at JAG, Diana Ferrari, Mathers and Williams, between 31 March and 1 April 2010, if you are a Fusion card holder. If you aren't already a member I would suggest just joining in store.
Not valid in clearance and DFO outlets.
Not available in major department stores or individual retailers.
Offer includes already marked down items.
Can be redeemed multiple times during the promotion period.
Not redeemable for cash or gift card purchases, against prior purchases, lay-bys or in conjunction with any other promotional offer.
I myself might take this opportunity to buy myself some Winter boots from Williams.