Lamp Module will work fine for incandescent strings, but not for LED strings. The local control function keeps LED strings well lit, even in the OFF state. Appliance Modules have local control also, so they work no better with LED lights. You can plug 7 watt night light into an appliance or lamp module to shunt the local sense current and get a LED string to completely extinguish when OFF, but you can also use "Socket Rockets". The Socket Rocket has no local control, so LED strings are dark in the OFF state when controlled by a Socket Rocket. (I don't know why I am blathering about Socket Rockets since I doubt you have them in the U.K.(?).
FWIW
Probably telling you what you already know, but X10 can not be used to set Christmas lights to music. Protocol is way too slow.
BTW nice display.