Pixmania have the 2, 4, and 6GB Sandisk Sansa MP3 players, similar prices to other outlets, but they're including a set of Koss Portapro headphones for £1 as a promo pack. Now they do sell the headphones for £51, way over the £25 price I've seen elsewhere, but all in all the promo pack looks quite a saving if you want something other than out-of-the-box earphones.
These players use microSD cards too (about £18 for 1GB).
Reviews say that you can only put music on the card, but the user guide says music and video.
Use Quidco and other vouchers to bring the price down.