Freelander 2 cranks but wont start - intermittently

I have an 07 2.2 TDi 07 (205k miles !!).
I have a recurring but intermittent issue, that has meant 3 AA call outs so far !

The engine will turn over, but won't fire.
A bit of history -
- 1 month ago, filled up with petrol, realised at the pump half way through then had it pumped out - no issue
- about a week later, it took 3 / 4 attempts to start. Warmish engine, turned over but just wouldn't fire
- a few days later, first thing in the morning, same issue but would not start. Eventually battery died. I charged up with trickle charger & it was then ok
- I kept charging now and then thinking it was a battery issue, car was ok
- Few days later, same issue. Drove somewhere fine, parked up, engine then would turnover but not start. AA man came, could start the car with easy start, but no gas coming from the throttle. AA recovered to my local garage - they saw loads of faults logged and believed it was an immobilizer issue triggered by low battery.
- Few days later same issue, had been driven to our local village, parked up. Then it would turn over but wouldn't start. AA man called, he charged with his battery pack and engine fired okay. He did tighten and clean battery terminals saying that was the problem.
- Few days later, same again. Fired fine first thing, drove 15 miles, parked up. Few hours later, would crank but not start. AA man came, again could get it to fire with easy start but no gas from the throttle. He looked at error codes, and nothing immobilizer related. Needed towing again to the garage
- LR garage are saying they can't see nothing wrong. After charging up, fired straight away.

The battery is about 2/3 year old and has been tested as fine. Holds a decent voltage @ 12.4v
(After reading some other messages - I think tank was 3/4 full)

Pleeeease help.

Have any codes been read? Random failure to start can often be traced to a fault throttle body, when the butterfly doesn't fully open to the run position.
I'd get a full systems code read, and see what comes up.

If the battery is showing 12.4V, then it's considered discharged. These vehicles are very power hungry, and will flatten a fully charged battery in a few minutes if the engine isn't running.

Thanks Nodge.
The car is at a LR specialist now, and they're reporting nothing significant regarding error codes. I've asked them to keep it to try and replicate the issue. The AA man did a reboot on Fri though to clear fault codes to try and start.

I did consider a new battery, but everyone is telling me the battery is good (Garage & AA man).
The AA man used his battery booster, and the engine would turn over fine but still not fire. Could a low-ish voltage before he got there have triggered something to prevent subsequent firing - that the battery booster pack doesn't fix?

Additionally, there are a number of other electrical issues that have surfaced over the last 12 months, sunroof, passenger seat electrics, entertainment system (intermittent).

Thanks for your help.

Why does the LR garage and just try a new battery which is simple and see if that makes any difference, also maybe add the extra earth wire to the starter motor bolt, then remove the throttle body and check the butterfly and the cogs inside, another simple job, seems these so called LR specialists are NOT

Thanks Arctic. The battery swap would only prove something if they can replicate the fault, which they currently can't (speaking on their behalf).
I will definitely mention the throttle body, that seems like a possible candidate.

To round out this thread (hopefully) - the garage took at look at the fuel. There was 20 odd litres of PETROL still in the tank! The FL2 has a saddle fuel tank and according to the garage, cannot by completely emptied by sucking.
I'm now trying to claim against the fuel removal service.