Well I checked the pins for the power button for continuity when I pushed the button and got nothing so I knew it had to be the keyboard. I popped off the power key and carfully removed the little rubber button. This left the actual contact exposed and pushing hard on this powers up the machine. I just glued in a very small piece of plastic to the underside of the key and now I can use the power button again :) I guess a bit of liquid did just get into the power button so actually, a new keyboard would have sorted it.
Well I have it mostly working now, when I plugged it in I noticed a ticking sound coming from the middle of the logic board. Then I noticed an inductor was blown. Replaced it from a parts board and boom all worked great. Only thing now is the battery doesn't work, or something in the path to the battery doesn't work. The battery status has an x through it and it says there's no battery found. Any ideas on this would be appreciated.