Just as the title says, if you choose the tshirts priced at £3.99!
If you choose the £6.99 tshirts it's a little more expensive, but £7.98 is still deducted from your bill. Postage is £2.05, so excluding that it's 3 tshirts for £3.99.
Some of them are really nice!
Hope someone uses this - I have!
EDIT 8/1/09: YIPPEE!! All three T-shirts have arrived this morning!