This thread starts with `here is my solution, could you advise how to do it`. I would ask why you need a second CU and what circuits will be fed from it?
If you tell us what the circuits are to supply and what you have now there may be options available which don’t need Messing about with your current cu.
You have had 8 pages of advice yet nobody here knows what your requirements are. To advise we need to know what you have and what you need. A picture paints a thousand words, so could you post a photo of your current installation?
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