Can I just turn up at the UK consulate to get something certified, or do I have to make an appointment. 

Some documents are only dealt with by post, if you need to go in person you need to make an appointment, be aware that some items cannot be certified by the Embassy.

 

https://www.gov.uk/guidance/notarial-and-documentary-services-guide-for-thailand

Thanks theoldgit. I guess in an emergency one could get in though.

 

I see the appointments are made online now. 

9 hours ago, MrPatrickThai said:

Thanks theoldgit. I guess in an emergency one could get in though.

 

I see the appointments are made online now. 

You guess very wrong, how much of an emergency can getting a document certified be particularly as you already know that you will need the service.

 

If it's document notarising that you need doing, going to a lawyers office will be quicker and cheaper and may not need an appointment.