There has been some great feedback here guys and all sooooo helpful! All my boss wants to do is quickly me along and cheap cheap cheap! With absolutely no understanding where he's been off the tools for so many years!
So ive taken all of your knowledge and suggestions and think ive decided on an engineering judgment on how I'm going to move forward on this project!
1 - 434.2 is gold here because well... I really don't want to work with cable bigger than I really have to!
2 - MCCB Incomers - Ive never had to consider before and this allows me to comply with the above whilst protecting my DB main switches
3 - I can be cost effective in that two separate MCCB enclosures is apparently cheaper than the Ryefield (which is about a grand according to the boss)
4 - I can be time effective in that making all the links for a Ryefield is time consuming. (im sure you can probably buy somthing prefabricated)
5 - I will use a 100amp MCCB Incomer for the HVAC DB, a 125 Amp for the Main DB
You have all been absolute stars and a great response for my first posting here! Ill have to grab pictures of the final product!
Play safe out there!