ECN Forum Forums General Topics of the Trade Non-US Electrical Systems & Trades U.K. Building Regs. Part L - Energy conservation

Don't you really mean "English and Welsh" Building Regs? For comparision the (sensible) Scots regs say:

Artificial lighting

A minimum of 50% of the fixed light fittings and lamps installed in a dwelling should be low energy type.

The fittings may be either:
• dedicated fittings which will have a separate control gear and will only take fluorescent lamps (pin based lamps); or
• fittings including lamps with integrated control gear (bayonet or Edison screw base lamps).
e.g. tubular fluorescent and compact fluorescent fittings (CFL’s) with luminous efficacy at least 40 lumens/circuit watt.

...
• low energy light fittings include the provision of lamps/bulbs.