@EthanMenace fitted the recoded BCM but that has not cured the starting problem.
Before we swapped out the BCM the dashboard was showing an error message that said "Electrical fault". That message has now disappeared. Before we removed the old BCM the OBD2 port was dead and not transmitting any information. It is now working.
I wondered whether the key card or the key card reader could be knackered as the key card allows you to unlock the car by using the keycard buttons but it does not unlock when you use the proximity sensors on the full fat doors. I read online, in several places, that if the battery on the keycard is replaced or the battery on the car is disconnected you might have to start the engine for the keycard to work in handsfree mode. Also, when the keycard is put in to the slot there is no "keycard not detected" message on the dashboard and the steering lock does unlock. I think that the keycard is working fine. There is another keycard for the car but the bloke who we bought the car from has so far given me a few excuses why he cannot post it out to me.
So, if the keycard is working, and the BCM is working the electrical fault must be elsewhere. We did do a quick check of the fuses and relays before but now I think we will spend Saturday checking the UCP, the fuses, the relays and finally unwrap the wiring loom to see if there are any corroded wires or connectors running from the engine bay to the UCP, BCM or ECU. I am hoping that the UCP from the cup can just be swapped over to the new car.
When
@EthanMenace swapped the suspension out he found that the passenger side drain hole was full up with mud and was more like a clay material that dirt and mud. This makes me think that some of the wiring and fuses could have been affected by water damage.
The one thing that confuses me about the engine not starting is that it was working when we bought the car, it suddenly stopped working, and after a period of time I managed to get it started again a few times before it refused to start again. I am hoping that the randomness of all of this is down to a corroded wire or connector.
I will connect the car up to CLIP at some point to double check that there are no issues with the TDC sensor and code out the airbag lights that we have on now the standard seats have been removed.