you really need to engage a well-recommended local electrician who is a member of a self-certification scheme, because fitting a new CU is notifiable work (by law) and it will work out more expensive if you DIY it and pay the local authority, and especially if you have to buy or hire the specialist test equipment and learn to use it.
choosing the CU is the least of your worries.
If you buy one and then later engage an electrician he will be peeved because it might not be quite what he would have recommended, and as he will not be able to make a profit buying it on his trade account, he will winch up the labour cost to compensate.
that said, if the CU is in garage or workroom, a metal one will stand up better to things accidentally banging into it. Memera 2000 is roomier inside , and more rigid, than 2000 AD range, especially in larger sizes. If you decide to get all-RCBOs it will be expensive, but you then can use a 100A main switch and do not need (or want) an RCD as well. If you have some RCBOs and some MCBs, you need the MCBs to be protected by an RCD. It is worth buying a very large enclosure as it gives room for future expansion (mine is a 22-way, IIRC, though I am only using about 9) because a larger enclosure does not cost much more, you are just buying a bigger box and some fresh air. You can buy the MEM RCBO pods separately and retrofit them to MEM MCBs as long as they are not the AD range (I have found the pods fit on MCBs that have the green/red flag window, but not ones without) to assemble any rating you need (not all are kept in stock ready-made).
MEM is a premium brand and not all outlets sell it. Anyone that caters for industrial and commercial is likely to, as it used extensively where reliability and quality are key. The industrial "Memshield" MCBs and RCBOs fit into the lighter Memera enclosures (but not the other way round)
