I reckon the dimensions are the same; the differences appear to be cosmetic; different plastic moulding on the back, slightly different headrests. The rear tailgate of a T6 is quite different but that shouldn't affect the seat.Thanks guys, I'm looking to source a bed so wanted to understand the T5/6 differences. I'll be ringing round next week.
Shout if you need any photos. An excellent bit of kit IMO; very solid, useful storage cupboard underneath, two ISOFIX seats, seat belts, etc.
Be aware that the top of the seat (which folds flat) has a pair of seat belt housings that are higher than the rest of the seat; so a Cali rear shelf has two cut outs to accommodate them when you fold it flat.