1. (the main question!). I'm proposing the following circuits - does this plan sound sensible? BTW total floor area is 70m2; CU is a Volex split-load item: http://tinyurl.com/7fe6m (Screwfix 82204). So:
Non-RCD protected: a) upstairs lights, 6A MCB, 1.5mm T&E cable b) downstairs lights, 6A MCB, 1.5mm T&E c) linked smoke alarms, 6A MCB, 1.5mm T&E d) downstairs ringmain feeding specifically the oven, fridge-freezer and gas combi boiler, 32A MCD, 2.5mm T&E cable
RCD protected: e) upstairs ringmain, 32A MCB, 2.5mm T&E f) downstairs ringmain - all sockets other than those in circuit (d) 32A MCB, 2.5mm T&E g) electric shower, 40A MCB, 10mm T&E
I expect circuit (d) to cause most comment?! I don't see the need for a dedicated cooker circuit because I'll be fitting a built-in single oven with 13A plug (plus gas hob), which could be plugged into an ordinary ringmain. OK?
2. I've got some spare 1.0mm red/black cable which I'd like to use up - would there be any issue with me mixing-and-matching 1.0mm and 1.5mm cable within one installation (I don't have enough 1.0mm do do the whole house)?
3. CU is under the stairs, which means that the route for all cables will be running under the stairs, in a straight line, at ~45deg, in the space created behind plasterboard attached to battens on the bottom of the stairs (clear?!.) Now, if the plasterboard were 'ceiling', that arrangement would unequivocably be perfectly OK; however if it were 'wall', it would definitely be unacceptable because the cables would be well within 50mm of the surface. What I'm unclear about is what does a 45-deg-mounted surface count as - ceiling or wall? I think it's ceiling, but I'd like reassurance that some future inspector isn't going to throw a wobbler at it! Not sure what to do if it's unacceptable as it is.
Thanks a lot David