I dont know what offers they have on offer at the moment but HMV and Argos always seem to have free docks/ itunes vouchers offers. Also Argos keep haveing spend £50/£100 and get a £5/10? Argos voucher.
Might be worth checking out, I think may be checl out the reviews for any free docks the differnt stores are offering, and see which odck gets the best reviews.
HMV in town today had free accesory pack (cleaner and a load of charging cables for car and home), £15 itunes voucher and £10 HMV card with the ipod touch.