Most hotel chains have a published rate but almost NOBODY pays it.
Try phoning Hilton and asking for a special rate and see what they say.
Also look for Hilton breaks where you can often book 2 nights for less than that.
I have often stayed at Hiltons for 2 day breaks where I have paid about 60 pounds each for me and my wife, which also include 1 nights dinner.
Here is the Saga site where you can book cheap Hilton breaks if you are over 50.
http://www.saga.co.uk/travel/general3/hilton.a sp?bhcp=1