take a piece of laminated MDF or similar as used in kitchens
lay your CU on it and mark through the holes in the back of the CU (and the points for fixing screws)
Cut those holes in the board
fix board to wall with 50x50 battens
If the board is rather larger than the CU, then cables can be led in easily and look neat.
If you use white laminate it is easy to clean and looks OK. The laminate surface is also insulating and will not support a flame.
If the wall is not flat you can space out the battens (you should only need to pack out one of the four corners).
If the wall is soft and crumbly you can use big screws for the battens in any convenient position, without worrying about where the fixing points for the CU are.
It is also possible to space things 15mm off the wall using screw-caps from Coke bottles or similar, passing the screws through them.
If you need to find a tradesperson to get your job done, please try our local search below,
or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Please select a service and enter a location to continue...
Are you a trade or supplier? You can create your listing free at DIYnot Local