Hi wanderer,
The LHR Sofitel is connected to T5 by a walkway so it is very handy;
http://www.sofitel.com/gb/hotel-6214...ow/index.shtml
I do not know their room rates for the day.
Other hotels ( the LHR T4 Hilton does day rooms) would be accessible by taxi or bus ( or you could take the Heathrow express to T123 and change to T4 for the Hilton)
On Bath road ( north of the northern runway ) you have 2 Sheratons, a Radisson ,a Marriott and a Rennaisance amongst others.
Regards
TBS
PS; The concorde room does have 3 cabanas ( private rooms) but I do not know if it is possible to book them for 9 hours. Whilst the CCR is nice, at the end of the day it is an airport lounge and you might well be more comfortable in a proper hotel room