Having finished the current job on my twin and it being sat in exactly the same position for two months I decided to tackle finding possible leaks, starting at the top.
After removing the tank the first I found was a drop of oil hanging off the tank return banjo (bearing in mind I haven't run it since November) so whipped that off and fitted two new Dowry seals, then cleaned as much old oil/muck off the engine as possible (4 cans of clutch/brake cleaner).
Removed all the rocker feeds and found the rear exhaust and front inlet fibre washers had collapsed, replaced all four with strange size Dowty seals I had that were exactly the right size. next was off with the two accessible valve caps and the rocker caps, these looked to be sealing well (put a bit more tension on the two under the UFM) then found the timed breather banjo loose, feed and return banjo's were also not tight enough.
Next day there was oil under the bike in two places, one was coming from the crankcase joint which when I checked the nuts holding the front stand plates on these weren't properly tight.
The other was below the bend in the feed pipe, now this one was really sneaky, it was coming out at the back of the rubber hose where it is on the the steel pipe by the top of the timing cover and running down the back of the pipe, the ferule wasn't a crimped one so wasn't sealing. rather than rip the whole thing, off as temporary measure I fitted a thin Jubilee type clip behind the ferule.
A week later and there is no sign of any leakage, of course I haven't run it yet but that is at least four leaks fixed
three of which leaked even without it being run.