Engine management light came on two days ago so took it to independent garage to read the fault code. It is P1136 additive mixture to low, they rang around to find out why this was happening on a 1.8t petrol when usually it would be a diesel that would generate this code including Chapmans skoda dealer in pickering but didn't get very far with them. He has reset the light and says if it comes on again to take it to skoda dealer as they can track it further with their equipment. Any thoughts or is it just a hiccup.

Therin lies a lesson I think -

Not all garages are equipped to read VAG codes and in this case I think your man has made a mistake and been on a wild goose chase.

You have a very common fault on the 1.8t.

17544/P1136/004406 - Ross-Tech Wiki

I'd suggest a search here and it'll reveal a nice little pictorial and guide on how to fix your problem.

Lean at idle, likely to be an air leak.