M and M Direct have a number of Under Armour items at big discounts at the moment. A number of T-Shirts starting at £2.79, polo shirts from £4.28 plus plenty of other things at big reductions. Downside for most people is that they are mostly in small, but if that's your size it's a bargain. Delivery is extra, but FD60 code gives you free delivery over £60. Some decent Canterbury sports gear as well.
Edit: SQ24 is supposed to give 10% off as well, but can't confirm that as I didn't see the code (in the wrong place on HUKD)
UK and BFPO £3.99 however standard delivery is free when you spend £100 or more unless you have a valid promotion code.
Channel Islands £5.99