Thank you so much - I was pretty sure I should be ok - but my local sparky kept telling me to to use L1 and 2 - and I didnt fancy the "told you so woman" bit if I blew something up!
I am trying to replace standard plastic light switch with smart steel one but old switch just had two connections for red and black whilst new one got three. Tried using L1 (red) and L2 (black)- nothing. Used L1(red) and L3(black) (remembering to earth switch) worked but on/off upside down - can't i...