I consider myself fortunate not to have needed visa advice whilst living here, but I always read the responses that Tod Daniels provides, because they provide a massively important background of knowledge that one day may become invaluable. I am always impressed (a) by the speed of response (b) by the extensiveness and clarity of the information provided. Thai Visa Advice forum, and every foreigner living or considering visiting/living in Thailand, would lose out immeasureably if Tod Daniels wasn't doing this valuable job.
The only risk with using a sterling account, if allowed, is that if you don't keep substantially above the 800k baht equivalent, and sterling suddenly collapses (it has been known, 555) you might find yourself under the required amount.
When I did mine recently in Hua Hin, although I had the consulate letter, the pepple at immigration reception gave me their own form to fill in and present upstairs instead. (It is very similar to the letter).
may I ask a clarification; are you saying that if you have a non O-A 1 year visa, you can exit and return to Thailand as many times as you want without having had to purchase a multiple re-entry permit?
Could I also just observe that there are certain exceptions where a person with O-A visa does not require health insurance, for example, if the original stay in Thailand was based on a Business visa.