As kev says it could be one of your oil cooler hoses which are just above your oil filter next to the block, have a look round that area to see if you can see them leaking, if you want new ones from Ford the finis codes are 1639256 for the forward most one or 1643728 for the rearmost pipe. They are fiddly to change but only because of the tight space you have to get a screwdriver in to the jubilee clips.

Steve