nissan micra not starting up?

hi .when we had the bad snow over xmas my nissan micra 2003 m reg engine management light came on .a local machanic had a look at it for me .he said it was the engine chain .he turned it off for me .( anyway it came back on again )the car sounds quiet,not noisy at alll.anyway started having roblems with starting the car .but it would start eventually .but now wont start at all.the machanic rang a nissan friend to ask advice about it .anyway he said could be an immobiliser problem .the car turns over ok but wont fire up its just done 17.000 miles and was a good car till this happened .i cant afford to have unessassary work done on it just to find out its something else which alot of micras seem to have had done to solve this problem..i have checked fuses in engine compartment they are ok.tok out the fuel fuse .didnt make any difference at all.advice on this welcome ..thanks