Returning to the fork seal leak, as above I used the 'seal mate' not expecting much but I'd got it so worth a try (I bought it years ago when I had a leaky Ohlins fork and it did bugger all on that).
Rode to East Kirkby and the fork leg was pretty much oil free, amazed at this I cleaned it really well before returning and now that I'm home (around 120 mile trip) it's as dry as a bone/clean as a whistle so, definitely worth trying as the seal mate is cheap and only takes a couple of minutes to use.
So, for now at least it's fixed, no more oil leak - well, either that or it's stopped leaking because it's all leaked out...
For anyone that might be interested, this fork seal has completely stopped leaking (and I don't think it's empty) and my diagnosis is a strange one.
I have a fork travel indicator on this leg, essentially it's a yellow plastic ring with a groove that's held in place with a large 'O' ring and it was supplied by Ktech when they serviced these forks some years ago (it's a posh alternative to a cable-tie).
It basically stays in place on the fork leg to show you how far the fork has compressed and, I suppose it has it's uses especially when setting up the preload etc. though after the years mine have been set up without any alteration, I don't really need it.
Returning to the leak, what I think may have happened is that on the ride previous to me noticing the leak, I was riding quite 'enthusiastically' on a road that I'm not overly familiar with and that has a questionable surface quality with lot's of rough spots and potholes. I duly hit a pothole fairly hard that bottomed out the suspension. No big deal and no harm done (I thought) but I'm thinking that, in bottoming out the suspension the travel indicator, which is about 4-5mm thick has jammed into the seal and, either introduced some dirt or even 'folded' the lip of the seal inwards? because there was a decent amount of oil that had exited the seal but, after running a 'seal mate' around it a couple of times the leak has completely stopped.
To add, I've had a couple of sets of these Showa forks and never, even after many years service had a leak, unlike the Ohlins on my 916 which have, twice become incontinent and, maybe it's now time to get them serviced anyway as it's been a good few years since they were last done but I'd rather do them in my own time than be forced to do it due to leakage.
Anyway, if my theory is correct then there's a moral to this story which is; if fitting a fork travel indicator try to find a thinner/softer one, maybe a thin cable tie that would be less likely to get stuck into your seals than the rigid plastic version that I had (now removed).