SKODASGOOD

Thanks very much for the suggestions.
The problem has re occurred and left me stranded twice recently. Engine turns over,but no start.
Sometimes the SRS light comes on,but the engine managemant light does not.
Leaving the car and coming back to it 30 mins later made no difference this time.
I Really like the car and it has been the best ever for lots of reasons,but either I cure this or it goes,can't trust it like this.
So disconnected the ECU and reconnected no effect.
Removed instrument panel and re connected no effect.
Ran a diagnostic fault code check, no codes.
Thinking about low battery voltage,put a meter on it,but was showing 12.78v after everything on and 14.9 when charging on idle.
The battery is the original and now at least 8 years old.
Glad I didn't go for a new one!
One last major look at the relays,real pain to get at them.
This time I took the heavy cable holder off which is in front of the relay board to give better access,just one large torx screw.
I took all the relays out and replaced them(so I thought) no effect.
Then contrary to the book,removed and replaced them with the igntiton on.
As I replaced the large bulb sensor/relay,l(ots of beeping when it was out)there was a click and the engine management light came on,engine started.
The click was not from the large bulb sensor.
By moving the sensor a bit I could get the engine management light/ engine starting to come and go.
Another relay ?
Tucked in the corner behind the bodywork is the fuel system relay 469 black with 4 ordinary blades and a small one .5 total.    part no 6Y0906381
Seems this also feedsback to the ECU as well. It is a VAG/Skoda spare only.
I removed the relay case and the contacts were badly pitted,it would seem that the relay needs to reset when the igniton is turned off and it wasn't. I cleaned the contact with a nail file and replaced it,the engine started every time with all the warning lights showing as the igniton was switched on. Then just the engine management,charging/battery and hand brake,finally leaving the hand brake after the engine started.
Obviously I have replaced the relay.
The moral is find the right relay! The one I changed in ther previous post wasn't the fuel sytem relay Doh!!
Interestingly, when I rechecked the fault codes there were sveral caused by my live relay removals including one for ECU with wiring,fuel relay or fuel system as the possible causes.
Keeping the car and carrying a spare 469 relay.