HELP!

Hi, I've got a problem with my 4x4 Saph Cosworth.

Intermittant starting problem. Car will be fine for a few days then suddenly when I come to fire it up it wont start. Good battery and new fuel pump. Car turns over fine but just won't catch. All of a sudden it will decide to fire up and runs fine. Doesn't seem to be any set period of time it turns over without firing up: has been as short as 5mins with 10 attempts or as long as 3hours with 100+ attempts.

Also doesn't seem to be related to the length of time the car been running or if it's been on a short or long journey . For example it cut out today whilst driving on a short trip then wouldn't fire back up for about 10 minutes. After which it ran fine for 5 or 6 fire up's then came it start it after it had been stood for 5 minutes and just turning over , left it 2 minutes caught . Checked plugs not flooding plus also getting a spark .
I was just wondering if anybody has had any similar problem and any recommendations as to what to check etc. I've tried cleaning the sensors. I have changed the injectors, chip, map sensor ( gone for standard to 803's 3 bar map and uprated chip )and it still does it.

please help as otherwise it'll become a bonfire

Thanks guys.
Mike.