Do we need to earth the electrics in the loft in one go or can we do it room by room?

The fact that your lighting circuit has no circuit protective conductor (cpc or earth as its often referred to) dates the upstairs wiring in your house to pre 1967, and so it is now considered to be "life expired" i.e. its 50+ years old and it needs rewiring. You only have two options really i) leave it unearthed as it is, but you must only use plastic light fittings and switches (so no metal switches or metal spotlights) - please be aware though that if you decide not to rewire the lighting, its best to be honest and tell your house insurer and pay the additional premium they may ask for. I am only mentioning this as I have had a few cases over the years where old wiring has been identified and ignored by the owners and the insurance company has then refused to pay out years later, even on an unconnected fire claim! OR ii) best to be safe and rewire it to BS7671:2008 standards. To rewire the lighting circuit, will almost certainly require the some sections of the loft boards to be lifted up so that the cables can be installed, as its not really possible or cost effective to rewire it room by room, unless your willing to have the cables run on the surface of the ceiling and down the walls in plastic mini-trunking? You will also need to ensure that any fibreglass loft insulation is removed from directly around the new spotlights and that there is sufficient airflow around them. The spotlights must also be fire rated (i.e. have the F symbol on them etc) I would strongly advise that you take a look at the Electricity Safety Council website on the dangers of spotlights, as poorly installed spotlights often lead to house fires! http://www.esc.org.uk/public/guides-and-advice/ Finally please be aware that MR16 low voltage and GU10 mains voltage spotlights have high annual running costs and therefore LED spotlights are the best solution for both energy saving and reducing fire risks. Hope this helps, please click on "like" if it does

Hi. I'm not sure why (ie: in what way) the upstairs circuit (I assume you mean just the lighting circuit?) is not earthed. If it's not earthed due to a fault - eg: earth disconnected at some point - then it would be best to reconnect it, or otherwise locate & fix the fault. If it's not earthed because it was never earthed (ie: no earth conductor in the cabling - which I assume to be the case), then this would require a rewire. In the latter case, then you'd be doing yourself a favour to have the whole lot done in one go. It will be less expensive and less disruptive in the long run than doing the work a bit at a time. Also, you may struggle to find a reputable electrician who'd be willing to leave large parts of the circuit without an earth whilst fixing other parts. It really just doesn't make sense to do that. Hope that helps.

"The spotlights must also be fire rated (i.e. have the F symbol on them etc)" I thought the F symbol meant that they could be fitted to a non fire retardant surface, ie plywood etc, the other "fire rating" which I suspect is what you are referring to, is lights designed to not compromise the fire rating of the existing ceiling, which would only have to be used if the room above was designated living space, i.e a bedroom for example