The sound isn't so much people walking about, but the sound of things entering the w/c with velocity!
That is probably higher frequency sound which is likely to be coming through a hole or gap somewhere. If there are any gaps around pipes etc., seal them up.
To assist with locating where the sound is coming through, get a hosepipe and jam it under the toilet lid so that it trickles directly into the water. Then go downstairs and see where the noise is loudest.
Boxes around the lights will be very difficult as no access from above, they really need to be sealed to the back of the ceiling for best effect.
Make sure the lights are enclosed at the back (those linked to earlier seem to be), or ones like this:
http://www.screwfix.com/prods/72064/
(you can fit the CFL and LED lamps in those)
Lamp types are basically:
Halogen - switch on instantly, use vast amounts of energy, get very hot and don't last long.
CFL - last 10x longer, use 80% less energy. Don't get anywhere near as hot, although some space for ventilation is needed. Take up to a minute to reach full brightness, so no good if switched often.
Some examples:
http://www.nationallampsandcomponen...gy-Saving-Light-Bulbs/Megaman-CFL-GU10/34/278
LED - instant on (even faster than halogen), use even less energy than CFLs, practially cold in operation. Lasts for ever. Available in any colour you want, even ones that change colour. Decent ones are very expensive. Cheap ones are useless. Some examples:
http://www.nationallampsandcomponen...hting/Philips-MASTER-LED-Lamps/29/426[/QUOTE]
Cheers for all the advice everyone.
I logged on for some spacing advice and found I had walked into a minefield.
Have cancelled my order for 12v 50w downlighters from
screwfix and ordered 240volt 35watt as above with the option to repace the bulb to leds at a later date.
Ceiling plan is excellent , thanks.