Hi Bedds,
For starters, here is a link to a schematic of what is (hopefully) the seat that is giving you the problem...?
http://lushprojects.com/bongopartsmk2/c ... 2of02.html
You may find the problem may well be just with one of the release latches to the seat back? There is one either side of the seat & i think they are interlinked so you only need to pull the one side & both unlock to adjust the seat back??
Have you tried pulling both sides at the same time? It could be the connection between the two that has come adrift & not releasing the seat back mechanism on the opposite side...?
Sorry i cant help much more than this, i'm currently working on a similar problem with my wife's K12 Micra drivers seat.
Though in my case i've as good as sorted the problem...
Maybe one of the "converters" will know a little more about these Bongo seats?