Don't under estimate changing the Sump/Gasket. It is a bitch to get them to seal.

Where is the oil?? Bottom of Starter? If so, my moneys on a Split/Perished Oil Drain hose. If so, part with your £35odd to Ford for a replacement!!

Trace where on the engine it is coming from before wading in and taking stuff like Crank Seals and Sump Gaskets on IMO.