Do you mean the buggy where the seats are side to side, or one in front of the other??
I had a double buggy at one point, until my older daughter decided she wanted to walk everywhere about a month after buying it!! lol
I do still have it and have had it in the boot once or twice. Dont really use it now so am trying to sell it - I'd be happy with enough money for a tank of fuel
Anyway, the buggy is a Graco Stadium Duo - hence it has one seat in front of the other. It fits into the boot with ease - the boot really is bigger then I initially thought!
I would also still have room for shopping etc to go on top of it.
This is the pushchair I have......
If you can wait until the weekend, I'll try and take a pic of it in the boot if you want, to give you an idea of how much space it takes, and how much is spare for shopping etc?
In regards to the buggy - it was great! The back seat goes down flat, for a new baby - or you can attach the baby carrier straight onto the back seat - hence you dont have to take baby out of the carrier when putting him/her in the car etc.
Nevertheless, as I said, the pushchair fits in fine and leaves good space for several shopping bags etc.