You have really started up all the keyboard warriors, back to your original question. I had a similar issue from my Australian investments and tried to get a tax number from the local revenue office, they sent me to my bank and the bank sent me back to the revenue office. In the meantime I was informed by a friend that Thais use their Thai ID card number as a tax ID so you could use the pink foreigners card number,(also known as a refugee card?) which I applied for after getting a yellow house book. I have used that for my Australian investments for several years, and so far no one has questioned it, maybe good for the UK investment companies?
I was also told by a Hong Kong based investor that more and more countries are insisting on this, comes from the USA chasing it's citizens trying to avoid tax and other countries through tax agreements?