Is it better to apply for a Thai workcation visa from Spain or the UK?

In Spain it takes about 3 weeks, or at least that was my case. But they will ask you proof that you are legally living and working in Spain (even if for an UK company), such as (visa, work contract, etc.), and not only as a tourist being a digital nomad, if you know what I mean. If you want to do it from there, and you have all the required paperwork stating you do live in Spain, there should not be a problem applying from there I believe. Or to make sure, maybe ask them via email. They don't ever take the phone, but via email they may respond. No interview in my case, if that helps too.

In which country do you have the money, Spain or England? If, for example, you have 500,000 Baht in euros at a Spanish bank and you want a bank statement, it will probably be in Spanish and you won't be able to apply for it in London. You will then have to translate it into English, which may be difficult or expensive, or you will have to use a translation program.

It is all done online and you can be asked for an interview. London is fairly quick with approval often within 5 business days and going by postings rarely asks for interviews. You need to provide a contract of employment, detail how you work online for non Thai firm/clients.