sorry to sound like an ass but the answer is ZERO chance! At the very least you would need a full ATP that could be validated and then you would need hrs in a FAR/JAR 25 aircraft with at least 500PIC on said aircraft. Then that aircraft would probably have to be something thats not used much for the CAA to even consider validating you. e.g 1000hrs PIC in a EMB-195 as opposed to a 737 or A320 which every tom dick and harry in europe is rated on. It sux but thats the reality