A double socket near each corner is correct; also for walls over 3m long, a double half way along, or otherwise at 2m intervals.
If you put one each side of chimneybreasts, each side of (most suitable) bedhead, dressing table etc that will reduce the number of multiway adaptors
you buy later.
Also one at each end of hall and landing for the hoover and possibly a table light.
One where you will put each phone.
A bunch of them at worktop height where you will have PC, workroom and home office, and in the garage.
The alarms (intruder and fire) should not be on an RCD to reduce the risk of power to them going off.
p.s. having lots of sockets does not mean that will will exceed the circuit loads. It just means you have plenty of choices on where to plug things in. Most electrical appliances (hifi, table lamps, hoover, juicer) use very little electricity and are only on for a fraction of the time, and not all on together. The only heavy loads in domestic use are those with heating elements, especially tumble driers and cooking appliances, but also fan heaters, washers and dish/wrs. Kettles and toasters are high load but only on for a few minutes, unless you are running a B&B.