Brain picking time. Hope someone can help. Cheers

I have a my96 uk series McRae and It has starting problems, It is fine when it is cold but if you do a couple of miles and stop for a short time it will just turn over and over. If you leave it a bit longer it starts first flick.
I removed the cam sensor cleaned it and replaced it and she started fine. I did the same to the crank sensor and it just turned over. I removed the sensor again and replaced it and hey ho started first time. Verdict Crank sensor is getting lazy.
Is there a way to check the sensor and if so how, or do I just have to go and spend £120 and get a new one.
Cheers for any help.
Craig intermitantly happy and then pi**ed off again