As you know, there's the £10 voucher available to all on the homepage.
EDIT: Oops, my bad! Forgot the £10 voucher is over £50 spend.
Click on the link and fill yer boots.
Apologies if this has been posted before.
Cheap toner can be found on many places on the web also. If you have documents that don't need to be in colour, these things are great workhorses. IIRC, mine is up to about 8,000 sheets so I'm going to order another.