Hi unfazed, not sure what you mean about "if it aint broke dont fix it" because as I said at the start of the thread, the old one was leaking and now after replacement the new one is too still so seems quite broken to me. The seals wern't genuine yamaha ones though, I wasn't sure where to get them and didn't even consider it when I bought the seals from the wemoto website before I started this thread, an experience I will now learn from. To be honest though, the right side is not leaking at all so I don't think the seals are poor I think there is another issue which needs to be determined.
His dudeness yeah I think replacing both is the sensible option but the bike has only done 21,000 miles and the forks don't look to be damaged or corroded unless something is happening below the seal? Surely buying a whole new set of forks is quite a big (also expensive) decision when realistically couldn't I just replace the stanchion on the left, replace the bushes/seals and dust seals in both with genuine Yamaha ones this time and then stick in some new fork oil in both (15w as I used 10w recently and doesnt feel quite as firm).
DryRob okay cheers I will message him and see what he says but I don't want to rush into anything and have to spend loads and loads, for the moment its quite a small leak and the next MOT is due next June. What you say about the bushes is interesting considering the mechanic did say the bushes are worn. Also interesting, how come it wouldn't be advised to mix tubes and lowers as I don't really have a lot of experience with forks? Would it be because of different rates of wear? Thanks again for the tips everyone