Both keys don't work. On suggesting to the service adviser that it could be the immobilizer, he said that if it was something to do with the immobilizer, the green light in the console would blink when you put the key in.
There is a recall on the shield protecting the ECU. Make sure they check this area for corrosion. If bad things made it past this shield, then they could be messing around with your car's brain - and therefore anything could go wrong. Make sure you ask them to take a look at this!