I'm specifying the re-wiring of a house where there will be 21 downlighters, most of them on the downstairs lighting circuit. As the ceiling space is generally inaccessible, to get low-voltage downlighters (lower electricity bills, less carbon footprint blah blah blah), I have to have a transformer for each downlighter. This will cost an extra £8 per light, or £168 + VAT even with a trade discount.
In my bathroom, I can have one transformer per three downlighters, so it will be one-third the additional cost.
I'm reluctant to use the low-voltage lights because the extra cost will completely destroy the economic logic, plus any carbon saving is immediately made pointless by all the extra copper, other components and the carbon cost of manufacturing the transformer.
My question is: why can't I just have one larger transformer at the fusebox so the whole ring is taken down to 12V? I can then use a step-*up* transformer on the few lights on the downstairs ring that aren't downlighters.