How to safely connect multiple devices to one plug socket/extension cord?

So basically I'm wanting to surprise my mum and redecorate the living room for her. It will probably happen early 2017 as I need to save up and plan ahead, which is partly the reason I'm asking this question.
So basically there is one double plug socket behind the TV it has one extension cord connected already, one double behind the sofa, which already has one extension cord connected.
I want to buy a new TV, and maybe try and mount it onto the wall in the corner, but maybe this would expose all the cords behind the TV so I still haven't decided. I also need to keep the sky box connected but I will be adding a HDMI switcher and connecting a Sky box, a new Xbox, Playstation & Apple TV and maybe a DVD Player but that may not be needed as there is already thr Xbox and PS, or I will get a TV with mounted DVD player.
Next to where my mum sits there will be a docking station for her iPad the docking station is new and I will possibly be adding the Sonos system for surround sound for her TV and Music.
But because there is so much new electrical devices being installed, I need to know how all these devices can safely be connected without the plug socket blowing up, or setting the house on fire. She is quite up to date with technology, if I show her how to work something she will pick it up really easily so I'm not worried about wasting my money.

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