Have you changed the oil since purchase? If not, I'd do that ASAP and use a GOOD quality oil (do a search it has been covered ).
Depends on the leak, but mine has had a very small leak for years now with no troubles.
Solution is generally to replace the rocker cover seal.
(airbox out, rubber bend and AFM off, plenum off, unscrew rocker cover bolts, replace rubber seal, re-install rocker cover etc) - fiddly job though due to piping at the rear of the engine)
Iain, looks like you need to fix the site again.