Ok so I visited my local GAME today, where I was informed that my 120GB Elite would net me £80 trade, and the old wireless G adapter would be £10. Shockingly, the guy instore said that these prices include the 25% bonus. Poor showing from Game and Gamestation.
Gamestop UK are offering £100 trade for an Elite against a Slim if you're near one of them, but HMV's £109.99 is the best i've found so far.