The Littles car restraint guy ended up calling back twice this evening - god i love good customer service- he is coming around at 7am tomorrow morn to install all 3 car seats - he says a Britax Hi-liner will fit in the car and can be used for DD whom is 4. We can then use my 1 x MR and my SNS rear facing one too...Phew.

He also said he's fitted 4 x car seats in the Odysseys before (3 in 1st row, 1 in 2nd row), so feel a bit reasurred now....