I have now changed the crank sensor and the car is working fine again. On the 2.2 JTS the crank sensor is at the front of the engine, below the oil filter. It isn't at the back of the engine where I was told by quite a few people that it was.
If the sensor plays ball, you can take it out from the top of the engine bay. Mine didn't though so I had to take the starter motor out to give me more room and had one person underneath the car with a screwdriver plying it out and me pulling it from the top. It's a very tight fit but you just have to persevere.
You won't get the connector off first because there's a blue pin clip that you have to pull out and you can't get this out as there isn't enough room so leave it on while you take the sensor out.
Once out, take the connector off, put the connector on the new sensor, put a bit of lubricant on the new sensor and then work it back in. It's a tight fit so doesn't just push in, you have to work it in. Don't just use the bolt to push it in either otherwise it won't go on straight.
Put the starter motor back on and then try try the engine and it should work.
It's a pretty straight forward job but a right pain in the arse.