I parked up tonight and noticed that the headlights dim when I turn the steering wheel.

 

I know that this is down to the draw from the pump, but is it normal?

Normal; at low speed/ RPM the power steering draws a lot of current causing the lights to dim when you're manouvering. Happens on my MkI Fabia and many others. Nothing to worry about.

Yes, normal.

Yes, happens on my 2007 Roomster, gather it's electric (electro-hydraulic??) PAS so at low engine revs and slow vehicle speed, wide modern tyres and heavy front-wheel-drive layout equals quite some resistance to scrubbing the tyres round.

 

My first diesel, a Mk1 Vauxhall Astra 1600LD way back in 1987, had unassisted steering, and yes, a lot of heavy twirling at manouevring speed, I later obtained PAS rack, pump, column adaptor etc from a breaking upmarket Cavalier, got them fitted (engine already had the additional pulley needed), great improvement, but dropped the mpg from 54 to 52, and eventually required the powertrain out and the bulkhead reinforcing, as the powered rack was trying to tear itself free from the bulkhead! (fault discovered by astute MOT tester).

 

Also lengthy glowplug warmup required to start (indirect injection), and battery had to be in tip-top charge, gather the OEM starter motor feed cable was of inadequate cross-section.

Happy days!

Richard.

Yes, happens on my 2007 Roomster, gather it's electric (electro-hydraulic??) 

electro-mechanical I would bet.