Citroen Xsara Picasso car not starting

After continuous working car suddenly stopped and rescue service got mixed readings simply deduced computer management probably at fault. CAr towed to Somerset, local garage said often computer fooled by problems with electrical &/or fuel related signals. They kept it for a week, decided it was simultaneous high and low pressure fuel readings, purged line and rnewed filter, kept it a week, all seemd ok and yet a week later in slough vehicle suddenly stopped. Local friend has deduced following yet still car won't start..his analysis to date.... "Of the 3 seemingly important fault codes, 2 were fuel related & the other electrical and since the fault was intermittent; the electrical seemed the most likely. This was P1351 fault in Glow-plug relay.

The relay clicked in with key on, so I knew it was getting power.

I decided 4 of the connections must go to individual glow-plugs so checked the volts going thru; 3 were 13 volts and the other was almost none. I couldn't find the glow plugs till I removed the air filter and 3 sections of air pipe and used a mirror to look at the rear of the engine. I found the last glow-plug had the wire disconnected! With my finger tips I managed to find a matching nut and reconnected it. reassembled all the air filter piping etc.

Still won't start! still economy mode, still battery light on without even the key in.

I found a chunky ammeter and 3 glow plugs including the one I fixed take 10-15 amps but the other takes very little. It probably doesn't help it starting but I doubt that it causes the electrical faults.