I would be grateful for advice on cutting in to a caravan side wall to install a flush fit mains socket housing. The hole will be 13 x 7 cm.
What is the best way to go about it?.
One suggestions was to drill four holes, one in each corner and saw out the panel that way. Another suggested I put a hook up socket to the underside of the floor but don't want to do that.
Its a Lunar LX 1998 I understand the walls are like an ice cream wafer polystyrene sandwiched between two thin ply panels.

Many thanks

Bob UK, June 2017

Suppose I should have said it is a touring caravan and electrician tells me good ide BUT that fitting standard external socket will not only look cr*py but will possibly ingress rain when towing due to force of rain hitting socket when moving. These sockets are meant for use in static conditions not on mobile units. He wouldn't fit the recessed power unit nevr cut into caravan wall even though I have proper sealing tape, woried I would sue if it leaked water in to wall structure.
And if you have read
Thank you, thank you, thank you from the bottom of my heart.

bobuk, June 2017

An external socket should be either IP 56 or IP 55
They have lids...
http://www.rainfordsolutions.com/ip-enclosure-ratings-and-standards

It's a neat idea to have some kind of isolator switch on the inside to disable the external socket - Amazon will sell you one.

If you're concerned about the building regulations then have a sparky do the work properly.

Dvoid of any good wishes..., June 2017

Not good idea Goodluck, unusual for you.
Would look gross a socket assembly surface fitted
Possible contravene Part P
Dangerouse if accidentally suffered damage when live on site.

Bob UK, June 2017

Mount the socket on a piece of oversized plywood.

Fix the socket assembly to the ply - fix the ply to the caravan wall with a small hole for the cable to pass through. In this way you will preserve the integrity of caravan wall.

Forget about flush-fit.

Good Luck..., June 2017