The extremehoteldeals site has been running a series of well-researched articles on hotels which let you redeem for suites or high end rooms at standard rates. In some cases this may be an error, whilst in other cases it is simply the hotel trying to encourage more points bookings.
(EDIT 2020: the links below are now behind a paywall unfortunately)
Here is their Hilton list. The key one for the UK (apart from Conrad Maldives offering water villas for the usual price of land villas) is Hilton London Tower Bridge which is offering family rooms for the standard price of 70,000 points. These sleep four people.
The IHG list has two hotels of interest to UK residents:
Crowne Plaza Liverpool John Lennon Airport (photo below) – suite, with lounge access, for 20,000 points per night
Crowne Plaza Harrogate – suite for 20,000 points per night
It is worth checking the lists for any interesting offers in places you are planning to visit this year.
Hotel offers update – September 2021:
Want to earn more hotel points? Click here to see our complete list of promotions from the major hotel chains or use the ‘Hotel Offers’ link in the menu bar at the top of the page.
Want to buy hotel points? There are currently special offers running with Marriott Bonvoy (‘mystery’ 45% or 50% bonus to 25th September), Hilton Honors (100% bonus to 30th September) and World of Hyatt (30% bonus to 31st October).