Sounds like the keyboard circuitry has gone. If under warranty I suggest you contact the retailer. I am assuming there has been no liquid spill involved here but that is the most common reason for a keyboard to react like this.
Either way the keyboard should be replaced to determine if that's the fault - absolutely no point in "tinkering" with it. New keyboard should be about £20 I would think and probably quite easy to replace yourself. (Would need to check for you.)