I read your mind, I tried putting them in without removing the assembly, they seem to be in but not 100% secure (i.e they haven't clicked into place), just going to put in the ballasts etc and will tidy it up tomorrow. The darkness has arrived so everything now is being done by torch.
Thanks for everyones help today, I learned some valuable lessons ( one of which was not to waste time driving to shopping centre for cable ties, when they are included in the box.