Infant car seat safety - confused! - Lady Peugeot driver
Having tried out a couple of group 1 (9kg-18kg) infant car seats at my local Halfords I was advised there arn't any which safely fit the rear of my Peugeot 306 (1999). Apparently it's the seat belt buckle which could potentially 'pop out' in an accident. The chap was very helpful and called Britax for advise, however (contrary to Britax online 'fit finder' which recommends their First Class Plus model) their customer service centre could not recommend a suitable seat. We tried a 'Maxi Cosi' seat but it did the same thing.

I need help - my daughter is outgrowing her current seat and, apart from buying a new car, I need to find a seat which fits safely using a seat belt system. Is there a seat out there...?
Infant car seat safety - confused! - Westpig
Have you yourself rung Britax? For completely separate reasons to you, I rang them and spoke to one of the most helpful ladies yet. At least you'd know the advice 3rd hand via Halfords was correct, if nothing else.

Do a Forum search for a recent discussion on here re car seats. Whilst not specifically addressing your query, there was some good advice on it.
Infant car seat safety - confused! - AshT
I had the same problem a few years ago with a Primera - shape of the rear seats meant almost every seat tried led to "buckle crunch". In the end Mothercare fitted a seat which overcame the problem due to different fixings on the seat - I think it was a Britax, but can't remember which one I'm afraid.
I can recommend a visit to Mothercare though - I've always found their staff to be very good with selecting and fitting car seats.