Peugeot 406 Estate - pjg406
Thinking of attempting to convert my 406 Estate to a 7-seat model. Has anyone actually done this? Do Peugeot do a kit? What kind of leg-room do the seats allow. Does the spare tyre need to be taken out of the well? Do the seats fold flat to allow the boot to be used normally? Cost? Cheers
Peugeot 406 Estate - gsb

You could look at www.motorhoods.co.uk and their option 7. (I originally saw this info in H.J. in the Telegraph)
I bought one 4 or 5 years ago for my wifes 405 est.
Did the job well while children were small as no footwell.
It was not foldable but only took a few minutes to take out if all of boot needed.
Peugeot 406 Estate - Bill Payer
Sorry, didn't see this earlier.

I had a 406 'Family' version for a few mths (temporary company car). The extra seats do fold flat but the spare wheel was a 'space saver'.
We never used the extra seats - you get 2 separate seats (ie not a bench) but they fold up and down together. They were smallish but the most obvious issue was they were fairly flush to the floor, so no room to dangle legs (similar to the seats shown in the link that gsb provided in his post).
You'd obviously also have to fit belts - don't know if they use existing mountings or are specially fitted. Also the rear door had a catch so it could be opened from inside (maybe this is some kind of legal requirement?). Also the rear seat didn't have a split back - 5 seater versions did - again maybe a safety / strength issue.
I would have thought that many kids would get travel sick facing backwards and they're likely to get bounced around sitting so far back. I'd also be pretty nervous about another vehicle rear-ending me with kids in the boot space - if they'd slightly wriggled out of their seat belts they'd go out of the rear window.
While anything is possible, I would have thought that fitting this conversion using new Peugeot parts after the car is built would be pretty expensive. Wild guess - £1000 ish + fitting if not DIY.