Still no reply from the embassy. I called them. The Thai staff were not very helpful. I guess they were very busy and phones were an interruption. Eventually, I was put through to a British member of staff - Mr Callum Stevenson. From here on, things got less stressful. Mr Stevenson was very helpful. He quickly confirmed that my passport could not be used. Which, basically meant I was stranded in Thailand until I got a replacement. I was due to return to the UK in 2 days!
I booked a flight for the next day with Nok Air, departing Udon at 07:30, arriving in BKK an hour later. We'll see how I get on tomorrow.
I phoned JimboPSM and Doug today. We'll meetup some other time.
C'est la Vie!