Was just in Tesco shopping and picked up an electronics leaflet, seen they have a Logitech EX110 Wireless Desk Set, which includes a wireless mouse for only £11.99 - reduced from £24.97
Seems like a good deal, Logitech are a pretty good make & the next cheapest I can find online is £20ish
Had a look for the deal online and it's not on the Tesco website, but if your instore it's in the Back To School offers so I'm sure it's Nationwide.
EDIT: They also have Logitech speakers, model LS112.0 for only £9.47 - probably not the best quality, but good if your looking for some for holiday or something might do the trick.
(>> Thats the model in the pic)
Found at Tesco Metro: Manchester today 26/08/09 in the reductions area for £8.99 yellow stickered.