1 ring for lounge (lots of power need here and only 2 double sockets at present)
Lots of power, or lots of outlets? Have you really got several kW of load in your living room?
Ditto the master bedroom?
Is this doable within the regs or does a ring have to cover a certian square meterage?
You may have as many circuits as you like - the guidelines specify a maximum area served by socket circuits, not a minimum.
And don't get too hung up on the idea of rings - if you're having lots of circuits then you almost certainly won't need the capacity of a ring, and radials are better for future modifications.
Good idea to put all wiring in conduit for ease of future changes. And if you specify metal conduit for switch drops, or BS 8436 cable it removes the need to have RCDs where you'd rather not.
Think hard about where to have sockets - it's difficult to have too many, and also about what circuits to have. The items on the list below won't all apply to you, but they are worth thinking about:
- Upstairs sockets
- Downstairs sockets
- Kitchen sockets
- Circuit for appliances
- Cooker circuit
- Non-RCD circuit for F/F
- Non-RCD circuit for CH boiler
- Dedicated circuit for hifi
- Dedicated circuit for IT equipment
- Upstairs lights
- Downstairs lights
- Immersion heater
- Loft lights
- Shower
- Bathroom circuit
- Alarm
- Supply for outside lights
- Supply for garden electrics
- Supply for shed/garage
Plus any peculiarities brought about by your house layout & construction - e.g. in mine because of solid floors and where the rings run, I have a radial just for a socket in the hall, the doorbell and the porch lights.
Unless you want to go to the expense of RCBOs throughout, the CU should have at least 3 sections, 2 on RCDs and one not into which you can install a mix of RCBOs and MCBs.
If you live somewhere where supplies are dodgy in the winter, have the lights, the boiler supply, and a socket in each room wired to a separate CU, or a separate section in a large one, that can be supplied by an emergency generator - lights, heating, TV and a kettle/microwave make life a lot more bearable.