I have seen this problem before and usually 150+ is the price on offer and its almost always an RTB job for a new motherboard. I would advise you either break it down for parts and ebay it or try to sell it as is. A new laptop can start at as little as 299 so it really doesnt make much sense as the old machines hard drive ram and processor should fetch at least £100 if not a good bit more depending on the specifications. Alternatives are putting it in the local free ads etc. If it was just out of warranty I would suggest looking for ways around it but at 2 years old it makes little sense.
However if you can find a motherboard with a working power unit on ebay you could try replacing it however it may prove hard to do as they are pretty annoying to put back together.
I hope you manage to fix the matter.
PC world wont fix this kind of problem as far as I understand it.