I probably phrased that wrong, and did the garage a disservice. I think they were implying that it wouldn't get through another MOT unless the problem got fixed, and I'm also doubting myself about the £700. Or it may be that they didn't give me the whole story as they were (as usual) extremely busy. I'll go and have a chat as per Paws suggestion. If 4 new injectors plus seals is all it takes and there aren't a load of other things on the way out then it has to be worth doing. As Ed says if the job does cost £700 it may feel like a lot of money, when you compare it to the potential cost of any replacement it isn't, and anything I bought would lose/cost 700 a year one way or another through depreciation and maintenance.