petrol 1.8 freelander engine warning light

What is your question?

Hi since my MOT and having some work done on brakes about month ago the engine warning light flashed for a second them went off again this got worse and more frquent I spoke to garage and they looked and said there was a bit of oil on spark plugs and head gasket that they sorted as was leaking a little. the head gasket was changes about 12 months ago. today the warning light came on constantly. I have checked the coolant and oil and they are fine Any ideas what is could be or what i need to look at next Thanks