Best place to start is with the Valve Stem Oil Seals. Get the one piece top hat type from Fords for about £14. They are easy DIY. You will want the spring compressing tool. Handy tip I was given is to push a rag around the side of the stem seal you are working on as dropping a valve collet into the engine isn't funny. Also remove the spark plus as it makes turning the engine by hand easier (to bring the piston to the top of the stroke so the valve doesn't disappear into the engine once the collets and seal are removed)

After this I would clear all your breather system out.

If this doesn't cure it I would start thinking about having the turbocharger itself looked at as the seal will start to weep after a while. Chipping my FRST saw the turbo throw the towel in within a couple of days