Short answer from me. No.
At 150k miles how many more mile do you expect to get from the car. there are high image bargains to be found but I certainly wouldn't buy a car with more than 70-80k miles on it and even then it would have to have full history and confirmation of any adhoc work completed..
The MOT failure is a bit of a glimpse into the future if that motor.
Ah, ok, do you know any decent units that are either made for fords or would fit the slot nicely or should I just take a trip to Halfords or the local Ford garage?