I had a Thai e-visa rejected in Australia because they asked for one middle NAME, not name(s), so I left off my second middle name. They said it did not match the name in my passport.
If you're going back to UK for a while after getting an O visa, don't forget to get a re-entry permit before you leave Thailand. I lost my second 12-month OA visa because nobody told me that I needed a re-entry permit. It clearly said "Multiple Entry" on the visa stamp so I assumed it meant multiple entry.