Oil & Diesel removal from cylinder head.

[PioneerSSM]

I just suffered a rocker cover oil leak. I did think for a week or so that the manifold was leaking, but investigation by main dealer revealed the gasket leak dripping small amounts of oil onto the manifold.
Unfortunately after I picked up the car from the main dealer, I was once again troubled with fumes ingression into the cabin. Further investigation proved to be number 1 injector leaking. Caused during the gasket replacement.
All fixed now, and I  have carried out a steady run of 20+ miles at a steady 2000rpm in an effort to rid the head of all oil & diesel residue. Most seems to be gone but still a trace evident from the engine at operating temperature.
Any more ideas on ridding myself of this smell other than striping & degreasing the affected area would be welcome,  or will it simply disperse over the next few hundred miles? Anyone with experience of this?

Many thanks

Steve