Hilton started a 40% off sale (rates are pre-paid and non-refundable) for Europe at the weekend.
Details here – you can earn 13% cash back at Quidco with these offers only – not normal rates.
There are some good deals:
London, Dockland Riverside (click for review)
London Gatwick Airport – (click for review)
Even if you cannot pull up your preferred property from the main sale web page, if you go to the booking process and select rate codes of PGGG08 (room only) or PGGGB2 (B&B) these rates usually appear.
For example, the Hilton at Heathrow Terminal 5 (review thread):