2.5mm T&E in 16mm OD conduit ?

[ban-all-sheds]

1) I'm battoning out the wall to install insulation / sound proofing and the existing 2.5mm singles in conduit are not long enough to reach the new sockets

2) I'm taking to opportunity to add additional sockets on the ring - thus 'splitting the ring'. with hindsight i missed out the vital bit "to add new sockets"​

Run the cables horizontally between the sockets, behind the boards?​