700watt dimmer, or use dimmable LEDs. i personally would use 4/5watt LEDs which would solve the loading on the dimmer and satisfy the global warming freaks. but by not using GU10s, the central heating bill would increase accordingly due to the lack of warmth generated by halogensif you had 9 50w downlighters on a dimmer, you may be heading for problems. Dont dimmers have to be derated by 50% when used with halogen fittings. Also, if you are putting these into a new build (extension) or refurbishment, you will have to check what the building regs say
I have to thank you old mate for putting me onto these, a friend of mine in the UK is a sparks and he was doing a job last week and asked if I knew of anything better than a downlighter, I sent your link to him and he told me yesterday he got one and checked it and the customer is well pleased, and wants to replace about 15 others he had.
So where do I send you cut mate