what could be wrong with my trianco eurostar boiler please?

Hi, firstly thankyou to anyone that can help
My boiler is about 6 years old, a Trianco Eurostar
The problem is it will start up but dies after about 10 secs and the red light on the control box comes on.
I have so far had a chap out 3 times but each time I part with at least £100 and boiler remains not working!
Ive been advised to get a new control box which I have done and problem remains the same.
At this point my trust in engineers is sadly nil and any suggestions to help will be more than appreciated. I really do not know what to do from here, I no longer have any local companies left to use! and quite frankly now Im broke!
Sorry to sound negative on poor boiler engineers, just not had any luck lol
Thanks again
T