Argos has DJ Hero in-stock for 89.99 cross platform - better prices online but this is the best high street price I've seen.
It gets interesting when you add the wirless charger - http://www.argos.co.uk/static/Product/catalogId/1500001801/partNumber/5669051/Trail/searchtext%3EDJ%20HERO.htm
- as this is 1/3 off (£13 instead of £20) which brings the total over £100 meaning you get a free £10 voucher - this was in Old Street branch but I guess available nationwide.
Better price online, sure, but this way you effectively get the charger for free and the game straight away for a very keen price.
PS3 and Wii available for 89.99