problems starting vauxhall vectra 1.9Cd ti (2005)?

My Vauxhall Vectra has so far cost me a small fortune whilst i was on holiday to the Isle of Wight and i am no nearer to the desired end result of having a car that starts without trouble.

It takes a good 8 – 10 seconds to start from cold, But a considerably shorter time if the engine has not been off for long!

It was suggested that first off, i change the glow plugs- this i had done using genuine Vauxhall parts at a total cost of £160 inc fitting.
PROBLEM REMAINED

Next off – I had diagnostics done on car and it threw up a (ERV?) valve – Note: the engine symbol light WAS on in the car anyway but my local garage chappie said it was not overly urgent to get this fixed until after my holiday. – Anyway, i had this replaced at a cost of £206.

STILL THE PROBLEM REMAINED.

So back to the garage i went.

Next course of action was to have a leaking injector replaced at a cost of £307. (just the one, as i was assured that i really did not have to replace all 4 as i had previously been led to believe.)
Now, when the injector was replaced i was told that this was very likely going to be the cure of my starting problems because air was getting into the system through a lot of carbon build-up and that a vacuum in the fuel line was not being maintained causing the fuel to filter back down the system hence the starting problems ( because the fuel was not sitting (in or near) the injectors upon start up, it had to find its way through the lines from where it had settled over a period of time….this made a lot of sense to me as a layman and i really thought that this would be the be all and end all of my dilemma and rapidly decreasing holiday funds.
I collected the car from the garage, and it started without issues…great. – drove back to my campsite and parked it for the night.

Next morning, although it did start…it was not as quick as i had hoped…..and it has gotten progressively worst to the point of being back to square with it.

So, after having all this work done i still have a car that has trouble starting from cold. However if i take it for a drive then park it and come back to it say, 15 minutes later and start it, it starts relatively quickly…..start it say, 30 mins later and it’ll start fairly easily but NOT AS EASILY…and so on….getting worst with the longer the engine is turned off for.

As i say, and based on the injector explaination given to me by IoW mechanics, it sounds like it is definatly fuel related BUT what is my next course of action.

Grateful for any advice you chaps can give me on this.

PS – i dont think the garage has ripped me off as the Engine light was on and would’ve need attention sooner or later and that my local mechanic had previously advised me of a leaking injector prior to my trip…as for the glow plugs? Maybe a waste of time, but wouldn’t changing these have been the first course of action for most folk?…i dont know.