I don't believe that their is a timetable declared as part of the TUPE regs, but clearly it is right that you need time for this. You should demand at least a week and if you want 2, demand that. Tell your employer that you wish to speak to your advisor, and you won't be bullied into a quick signing.
LOOK PARTICULARLY FOR ANY PROPOSED CHANGES TO YOUR PENSION ARRANGEMENTS. It is not impossible for the new employer over time to alter these (I'm afraid) but this is one area where privte sector employers have a tendency to try and save money when taking on public sector workers.