I agree about not declaring a Pan, though if ATC are not too busy dealing with something else, I see no harm in a polite and professional mention that you're passenger is a bit airsick and that is why you are returning before planned. It makes people aware but also *may* just get you down a little bit quicker.
Just a thought
On the topic of RT, I presume it is the same one for all licenses, CPL / PPL, if so, the actual test shouldn't take 2.5 hours! I think mine last about 30 mins to an hour and is fairly straight forward if you are used to UK comms (which I wasn't - as I had flown only in the USA before that point, which is quite different!), so I did quite a lot of reading before hand.
I suggest looking at
http://www.caa.co.uk/docs/33/Aviatio...917_LOCKED.pdf which is quite good as it also has playable audio built into it & the CAP:
http://www.caa.co.uk/docs/33/CAP413.PDF