Yes you can do more than one type rating during your JAA PPL(H).
I looked into for another instructor a couple of years ago and as long as you have done the minimum amount of training on one type and do the test in that type then you can complete training for further type ratings prior to completing the course. It wasn't overly clear but when questioned the CAA did want the subsequent type ratings done at a TRTO and the type rating writtens to be completed.
GS