Non starter - help!!

What was an issue with trouble hot starting (see post a few days ago), has now become a won't start at all issue.

4.6 petrol - with battery charged, engine spins and 'catches', toying with the throttle can get it going for a second or two but then it dies. On and on it goes until battery is flat and all the evil messages appear on the dash.

This is all very recent, most noticeably since a few days ago when i was filling up and got a fierce 'blowback' from the filler nozzle and the tank wouldn't accept any more fuel without burping it out. Since then I've had starting issues and so was wondering if fuel starvation is an issue but once it fires (on those rare occasions that it does) - all is fine.

Another curious thing that I cannot see is related, is that when the car is turning over there seems to be a lot of suspension activity, with the car bobbing up and down. (Rear bags changed a couple of weeks ago)

Fuel seems to be getting through, there is a very strong smell from the exhaust.

Any clues/ideas very much appreciated as I'm in the middle of nowhere.

Updated - After another 3.5 of hours on charge, the damn things starts first time and the suspension, which had descended to access height all on it's own, popped straight back up to normal. Revving well, no issues, no misfire or hesitation.

Turn it off, wait 15 minutes for the wife to get back in, straight back out and it won't start. It just cranks and while doing so the suspension drops down to access???

Battery flat again (new C31 1000 on way)

I don't have any electrical nous at all and I'm confused as to what is most likely wrong -

Fuel blowback a few days ago when refuelling, starting issues aver since, so might there be a blockage/starvation issue - or-

All the time it cranks fuel seems to be getting through as there is a strong smell of unspent fuel from the exhaust.

Won't this be causing me CAT issues or is that perhaps a contributary issue after a few hot start failures.

Any help greatly appreciated on this one

Another thought, (sorry to keep posting on my own query) all the reading so far suggests I need sync mate, but if the becm and the ECU were out of sync, would it be completely dead whan cranking over or would there be intermittent signals, enough for a few seconds of life.

I think I know the answer to that - I'm clutching at straws - a quick plug-in of a sync mate would be nice easy answer. i suspect mine may be more complicated.