non starting first thing when vauxhall astra has been standing overnight?

Vauxhall astra 1.6 55 plate sxi twinport petrol, I have been having problems starting the car first thing in the morning when car has been left standing, car will crank but will not fire. at first would take a few attempts and would start but not it is not starting just cranking over, the other week I was able to bump start it and it fired up but today I went to bumpstart it and it didn't catch, don't know if that was because I didn't have much power because previously was getting a push off my drive but today car was just parked on road.
once started in the morning, car will start throughout the day, its when its been left standing for 7/8hours+, car hasn't started today just cranking over,
fuel pump has been changed when problem first occurred but never solved it, all wiring has been checked from fuel pump, ignition checked, battery is fine, has had fuel service history, on last service in sept when it went to Vauxhall they did fuel washout that solved it for about a week and then was the same thing trying to start it in the morning, before it would take a few attempts but it has got worse and now just isn't firing. please help very frustrated now! as garage sent ecu off thinking it was that and it came back faulty, I personally think it could be fuel related but im not a mechanic and ive had enough now