Thank you everyone so far for all your advice - whether its G or nausea i'm feeling, I know its not pleasant and the sooner I can combat it the better! Haven't been flying since my original post so can't tell you if your advice is working...
Bsfish - you are so right about someone else doing turns and feeling the g more...when my instructor shows me a manouvre (like the Emergency break) its worse than when i then do it.
In answer to B2N2's questions; because we are focusing on steep turns, its throughout the trip. After an hour doing steep turns as well as practising turning onto headings (with normal AoB), I am indeed tired! Exhillarated and on top of the world, but tired! Do you think its just the stage of training I am at that I am feeling it worse than a more experienced pilot? Everyone tells me i'll get through this phase...
And I think it was Backpacker's note (sounds a fascinating lecture) about low blood pressure? I know my blood pressure is very good, so maybe that may be having an effect?