New build: Because  tungsten element bulbs are being 'outlawed' soon do i still have to fit a few dedicated 'pendants to keep Build' cont' happy.?? I understand that low voltage downlights do not qualify either. Do LEDs?? Its all confusing.  Gonna go for fire/ accustic in every downlight but unsure what lamps i should fit??????  

It depends how fussy your BCO is.

Officially you have to use fittings that will only take a low energy bulb and won't take an incandescent bulb. Low energy is defined as one that produces more tha 40 Lumens of light per Watt.  For reference a 50W low voltage Halogen down light produces about 800 to 900 Lumens. That works out at 900/50 = 18 L/W so they don't meet the definition of low energy.

In my opinion the only LED down lights worth fitting (in a kitchen for example) currently cost £40 -£60 each so are probably too expensive. Hopefully in the future they will be a lot cheaper. If you find any that are a lot cheaper buy one and test it alongside a 35W or 50W halogen.

Best bet is to fit downlights of your choice and try and find enough other places to fit Part L pendants and strip lights. These can't all be in cupboards. We ended up fitting 4 of these 18W wall lights in the living room to make up the numbers.
http://www.tlc-direct.co.uk/Products/FLC309.html

As for the downlights... I would test out a few CFL downlight bulbs to see if you can live with the slow warm up time. That's the only problem with them now. The good ones are plenty bright and don't flicker.  

Not all downlight fittings will take both halogen and CFL bulbs. So if it's likely you will want to fit CFL check that the fitting you choose will do. Note that some CFL bulbs are deeper than others. Sometimes it depends on the power of the bulb.

If CFL downlight bulbs aren't your thing I would fit 12V Halogen downlights and and transformers. Fit "IRC halogen" bulbs (eg Osram Decostar). These save about 20% compared to cheap halogen downlight bulbs - but thats still not enough for them to count as low energy according to the building regs..

Calculate- does that mean doing maths??
Dare I ask what the formula is or is that also in the ADL 1A??
Does anyone actually wanna see these figures/results on a self build?