I have been pestered by my wife to have a light in the front of our house. She in fact bought a 120W flood light from Aldi with a sensor which will switch it on at night when there is movement with three variable controls light level, movement sensitivity, and time it stays one for. I hate the thing but still had to but it up, however it's only plugged in so easy to get rid of it.
However inside the junction box you have assess to 4 terminals earth, neutral, permanent line and switched line so it would be easy to daisy chain it to other lamps. The bulb lasted 3 days, the replacement is a 5W LED which worked fine so there would not be a problem connecting other lamps to the same sensor.
OK only day two with the new bulb so don't know how long it will last, but the idea of running other lamps from same sensor does make some sense.
As to timers the simple plug in timer
is cheap at around £5 and since mechanical can't see any problem with LED lamps.
Most central heating units have some sort of timer again relay contacts so unlikely to be a problem with LED lamps. I did quick internet search and there are 100's of timers all which are 3 wire so would work. The only problem is where you want a two wire timer, in that case some power must go through the lamps and the type of lamp is as important as the type of timer. I would expect any lamp which states it is dimmable will work, point is lamp dimmers need to have some current to work so will not start flashing as a capacitor inside the lamp charges.
Two wire time switches don't tend to quote how much current will flow when off. I looked at the "
Elkay 2 Wire Master Push Button White" and it states "When used with some low wattage lighting, heating and ventilation circuits please ensure a capacitor of 2 microfarads (minimum) is fitted. Supplies of suitable Elkay capacitors can be found at your stockist (Ref PFCC-1)" I would guess many others have similar instructions.
Seems they are called "Power factor correction capacitors" and cost about £5 which does seem rather high for what they are. The name ensure they are suitable for long term use and at 50Hz they will clearly allow some current to flow which is enough to run the switch electronics.