Big (but small) sofa

ppg

bit of late reply but try Ikea if you can get there.

this Klippan is flat packed (quite big though & the 2 seater seems more like a 3 seat to me) & is self assembly (the top half comes off and then the arms come off) leaving straight parts that are easier to get through doorways etc. I think its supposed to be one of their best sellers.
http://www.ikea.com/gb/en/catalog/products/S69841363
its only £95 plus the covers which start at £25, the back is a bit low tho and may not suit everyone and it is quite firm.

Then there's these
http://www.ikea.com/gb/en/catalog/products/S59839817
I found the 2 seater uncomfortable tho for regular use and the cushions going a bit hard at the edge and pressing through the slatted base - no idea about the 3 seater.

Have read opinions that the Ektorp is quite comfortable and I think is self assembly also but not sure. I dont know but it may be that most Ikea furniture is self assembly.

Hope that is useful.

Rgs