Just got back from my local Asda (Wigan) and they had a atack of Scalextric sets all at half price.
They had the Start Set, which was reduced from £36.94 to £18.47
The Top Gear Set which was reduced from £89.94 to £44.97
The Street Pursuit Drift Set reduced from £97.84 to £48.92
Sold out online, so instore only. Good luck, hope they hve them in your local Asda