Sounds a bit like the same problem I had a few weeks ago , one of the ignition amplifiers had killed himself .if not read under..
Some things you can check out for yourself already ,
1) do you smell fuel when starting?? yes the ignition pump is ok , No its a gonner.
2)do the spark plugs light up?
3)Is every cable attached proper , sounds stupid but electronics and 155's are a nightmare they have a tendency to divorce themselves so now and then
4)Swith box ok , negative ground ok
5) Do a rain dance around your car he will like this and starts immediatelly (only kidding)
6) good luck
500£ isn't that a bit high does yar mechy use gold and diamant tools?
I paid 'bout 175€ for a complete dead engine brought back to live again alleluja(3x)