Thanks for the reply Jakob and Abbey
I tried removing/replacing the battery , still the same .
I had a sneaking suspicion about the power button alright as after a few months without use you typically come back to a low(blinking screen) or flat battery(wont switch on) .
I took out the four screws at the back and removed the plastic pcb housing , I gave everything a good clean and polished away a few rough edges on the metal with a multi grit nail file/polisher , once I put it back together it seems to be working fine again .
I didnt need to remove the pcb completely , I presume the serial connection is hidden on the component side of the board .
This was something I got cheap in Lidl , less than 20 euros if I remember correctly , still Im glad I got it going again and saved it from the scrap pile.