Hello all.
I hope you're all enjoying the festive shenanigans. I've been replacing halogen bulbs with lower power consumption alternatives. I've written it up here, if you're at all interested in my solution:

http://emmaandpete.com/cooper-acres/how-not-to-throw-money-down-the-sink-with-halogen-lights

It's a bit nerdy and wordy (~1250 words, hence me not posting it verbatim here), but hopefully someone will benefit from it.

Sounds like you have come up with an acceptable 'general lighting' solution and you will be able to see to sweep the floor or hunt for escaped carrot slices.

But did you get any task lights directly over work surfaces? IMHO that's where you really need light in a kitchen. If you depend on ceiling lights alone, it's hard to reach the same lux level without glare. Worse, you can end up working in your own shadow.

Posted By: tonyWhat did you do re air tightness?

That's something I'm working on right now. The old downlight cases were largely sealed, save for 6 vent holes in the top, but the MR16 bulbs were flush with the ceiling and it was pretty good. I have some thin sealant rings for the new fixtures, and I'm hoping I can repurpose the old cases into being new sheaths for the new ones - I think a Dremel or similar can cut them down to size so they'll just fit over the top of the new units, while allowing for heat venting.

Posted By: rhamduBut did you get any task lights directly over work surfaces?

The worktops are matt slate, and the under cabinet lights aren't bad - but they're not great. They're next on the list to replace. They'll be repurposed as under-stairs lights.

Posted By: CWattersInteresting you went for 11W spiral bulbs with E27 screw base rather than say 11W Megaman with GU10s.

I looked at Megaman and other GU10 CFL swaps, but length was an issue. 65mm was the shortest I could find, and there wasn't much clearance inside the existing downlight case. It makes sense that these downlights are designed around standard GU10 MR16 bulbs (55mm tall, 50mm wide), and with that in mind there's little reason to make them any taller...which was the root of my problem. Also, having the spirals in means there's ~20mm of bulb hanging down from the ceiling, which helps the light throw - rather than just filling a nice circle of light on the floor.

Posted By: CWattersYou can get downlights designed around the 11W Megaman

Ah, good to know! I like solution even more than mine - thanks, CWatters.