For 6mm2 T&E, I'd probably use independent 20mm oval conduits, 1 for each of the two cables, but I'd guess you would will need 32mm oval conduit it you really planned to put both equally in a single size. Mini Trunking and Conduit are universally Employed in cable management all https://mini-trunking90122.dbblog.net/697775/the-2-minute-rule-for-oval-conduit