Hello urleft,
I will have to put my hand up and say I am English. I will also add something to my earlier statement on the visa extension. A friend of mine extended his visa today, he's a Brit too, and he had this to say:
I went today for my annual retirement extension. They want to see evidence that you have money coming into Thailand on a regular basis and that you are spending it, irrespective of whether you have an Embassy proof of pension income letter or 800k in an account.
Whilst my wife and I were being attended to by the Immigration Officer (and I can recommend taking your wife, if you have one!) I overheard another English chap being sent away. He had an Embassy letter but no back up. The officers were saying, you need a bank statement, how about ATM slips? etc. He had nothing and they sent him away.
So the moral of this story is, whether you are based on Embassy declaration of pension income or 800k in the bank, take evidence that you have funds arriving from overseas and are spending them here.
Immigration have now changed the rules - this is the new requirement regardless of which method you use.