Need to fit a longer cable to a six gang extension do I need this? The 1.55mm http://www.ebay.co.uk/itm/All-White...t=LH_DefaultDomain_3&var=&hash=item3f44b92174 Or this http://www.ebay.co.uk/itm/131307568548?var=430605177252 which seems to be the thicker stuff. Looking for around 5-6mtrs.
Generally speaking, 1.5mm is more than enough for that sort of kit, and indeed anything you can plug in to a domestic socket... ... but how long is "longer"? Voltage drop is a thing, so worth mentioning, but unless the answer is "much, MUCH longer", then not entirely relevant. (and by "much much longer", I mean ~100m, and now I notice I entirely missed your 5-6m in the OP, so disregard, and yes 1.5mm cable is more than enough)
Yeah 1.55mm will be plenty for what you need it for. Bigger is always better. But 0.05 is like one strand so wouldn't make any difference.