Sorry for the late notice, as it ends tomorrow (09/03/2014), but I thought it was still worth mentioning as we so rarely get deals on modular sets (albeit older ones), so I was very excited when I stumbled across it.
"Save 20% on all full-priced Toys from Lego, Thomas & Friends, Fisher-Price and Board Games.
^In one transaction. Subject to stock availability. Offers not available in conjunction with any other offer. Offer ends 09/03/14."
Definitely valid online (free standard shipping for orders over $50.00, or some items available for 'Click & Collect' - free), and presumably valid in stores as well.