After speaking with our customer about this, we got some more details. The trouble with these particular kitchen units was they’re a white?melamine?(plastic coated) door and were in a conservatory so that the cigarette smoke and grease stains had been nicely baked in the sun!
The solution we recommended for this was Sola Lemon as the cleaning agents in this product will get at the stains without damaging the doors. However, as with most?professional?cleaning agents it’s important not to leave the solution soaking too long or let it dry out.