A few questions...
Firstly - I have channelled a standard lighting cable (1.5mm) from where my consumer unit lives to the garden ready for an electrician to wire up a decking light transformer. I have a nasty feeling I should have used 2.5mm cable instead… is this right? I put the cable in while my bathroom was being done so it is hidden under a tiled floor now!!
Secondly - some lights from the transformer will be at the other end of the garden (18m from the house) can I wire these lights into the transformer on a separate circuit to the others installed in the decking? How many circuits can you have off one transformer?
Thirdly – I suspect that armoured cabling would have a lot of resistance and reduce the wattage getting to the 18m lights. Would it be better to sink some metal conduit for the standard size wire you get with decking packs?