Look around your stret for someone building an extension and ask for the old kitchen units. If you were closer to me you could have mine, but Kent is a bit far to travel!
Try your local freegle or freecycle group on yahoo, after sussing posting rules you can put up a wanted post for your free kitchen units - you would have to collect though. Either that or a talk to a local kitchen fitter, who might have access to unwanted kitchen units.