Td5 Immobilised...

I've got a bit of a problem with an S-reg Td5 90. I took it to a clay pigeon shoot over the weekend and it ended up getting immobilised through the following:

1. Battery voltage dropped (assuming)
2. Engine management stopped engine from starting (warning light came on)
3. Tried to bump start it and it started but then immediately cut out (happened twice)
4. Went to put on a freshly charged battery and alarm kicked off. Since then it's refused to do anything productive.

We've got the EKA code which you're supposed to input the code through the door lock. However after trying the door they (parents) looked at the door hinge and found no wires going through so how would it work.

Does anyone have any ideas on how to solve this?

We got the EKA code from Green's (don't have anything to do with them), just by phoning up and giving them the registration number. So by having the code one would naturally assume that you can enter it manually.

Note we don't have the remote for disabling it.

Any help would be appreciated, would prefer not to have to bypass the immobiliser as it's stuck in the middle of a field. Likewise don't particularly want to have to spend too much money on it.

Thanks
Ed