Cheers all for the advice.
Fingers x'ed its not a gasket fail.
If it's coming from where you say it is and judging by the colour of the discharge, it's highly likely rust from spark plug bodies. It's common as the plug wells are big water traps if the drain galleries are allowed to block.
Before you remove the plugs clean out the galleries and if you can blow out the plug wells. Be sure to cover them with cloth before you do, so as not to cover yourself and your eyes in crap. By crap I mean grit and small stones as well as water. Once cleaned out thoroughly remove the plugs, before you fit new ones ensure the threads and mating surfaces are clear.