Their policy now is to point you towards the Non-Imm OA retirement visa. Not always what people want. Often people prefer to apply for the extension based on retirement (from a Non-Imm O) in Thailand itself. Plus they can be quite rude, and unhelpful if the day has a 'Y' in it. :)
those are embassies, and consulates, of OTHER COUNTRIES in the UK. Embassies are places that represent the governments of countries abroad, to those countries
The UK government is itself based in the UK (mainly for logistical reasons) and therefore feels that it doesn't need an embassy in the UK to represent itself, to itself.
Yep. Just going off what they told me at the Embassy. That they can delay the date of issue if you ask them to. Maybe not everywhere, but that's what they told me in London :)