On the column stalks, having done more research, it isn't an additional stalk for dim / dip but an alternative stalk set with an extra contact in the lighting stalk. The ones I pictured were from a C reg car so predate the dim / dip set up. From studying the wiring diagrams all the regular lighting wiring is common to both setups so the dim / dip circuitry looks like it could be ignored. However, some of the wires in the regular lighting circuit pass through different positions on the connector blocks. (I had this with Dedra lighting stalks where I had three different stalks with the same connector block but different wiring. Annoyingly if you plugged in the wrong stalk it blew the internal lights which was what I was trying to fix.)
Getting a UK, dim / dip stalk set may prove difficult. As an alternative I would suggest shifting the wiring pins on the new stalk set to correctly tie into the loom and ignoring the dim / dip set up. If the connector blocks are different, as the wiring diagram suggests they might be, you could move the wires to the block salvaged from the old stalk set so it plugs in to the loom.
All this also explains why early cars don't have the resistor mounted on the offside front suspension turret.