.... expert wanted!

I have an intermittent non-start problem on my Vauxhall Omega that has 
defied the ability of my 'pet' mobile mechanic to fix.  The Vx main dealer 
in Snorbens says they won't look at it unless I can present the car in its 
fault condition (but of course, I can't get it there if it won't start! .. 
and even if I got it towed to them, there's no guarantee it won't spring in 
to life on the very next attempt at starting).

I really need a (local) "guru" who understands what the ECU checks while the 
engine is turning over on the starter before it applies fuel and sparks, 
'cos clearly it thinks (at least) one of those conditions is not being 
satisfied ..

Local = Hatfield.  Can anyone help?

Please?