I love dimmers in the children's bedrooms and sitting room, BUT - most LED bulbs don't dim. The modern way seems to be to control sections of LED downlights with multiple switches.
Don't put sockets or switches right next to each other - a pain to line up straight with each other, and especially a pain if tiling near them!
Are you planning on wall mounting a TV? Great to have a power and aerial socket behind or close. The danger is if it is behind you may not be able to mount as close to the wall as you would like.
Ah yes - sockets behind furniture seem like a good way of hiding them, but the bank I have behind my TV cabinet I can't use due to the plug/adapters being too big to get the unit back to the wall (so use an extension!).
Plugs near children's beds are a similar issue. I hate these wall-wart adapters!
Stainless sockets look great- but need a bit more maintenance. Bog standard white switches are easier to clean!
A socket in the hall for vacuuming is great. Maybe sockets in built-in cupboards for charging things like cordless vacuums. A shaver / electric toothbrush point inside a bathroom cupboard hides the wires for those things.
Sockets either side of the sofa are great for phone / laptop / tablets etc.
I quite like wall lights - behind the sofa for reading, would like some in the bedroom too (but may go for a headboard / lighting thingy).
Do you have garden lights? An interior switch for them is great, I'm also considering putting in a switch upstairs to control them too.
Exterior waterproof socket for the mower is useful. Maybe an electric vehicle charging point too?
Get a bigger consumer unit than you need so if you extend, fit an electric shower, or put in a garden office it can be expanded without full replacement.
Check the output of USB points in switches. Modern phones with fast charging draw current more than the older USB standard (5A to 3 Amps I think) - so phones charge really slowly on the 'old' standard.