Had my '64 plate Metropolis now for 12 months and have really appreciated the 'luxury' extras compared to my previous MY12 HSE & MY07 SE, but the one thing that lets it down is the headlight main beam performance. I was really looking forward to the upgrade to HID lighting and for dipped beam driving they're great but throw the main beam switch and, well virtually nothing happens, all there is is a very week pale light thrown forward a few meters!
Am I right in thinking that the one HID bulb serves as both dip & main beam or is there a separate halogen main?
Is it worth the extra £150.00 + to upgrade the HID bulb to gain the improved main beam performance?
Thanks.

The later, MY13 on HID lamps are very poor, the earlier HID units where much better.
I have upgraded the HID lamps too, Philips extreme vision HID and can't say they are any better, beam pattern is dreadful and the beam spread is rubbish.
When I first turn them on they also go through a strange colour change before they settle down, I've had them out of the car and the reflector assembly etc is very poor quality.

I’ve just swapped a beloved ’57-plate HSE Td4 for a ’64-plate Metropolis Sd4 and there’s a shed- load of improvements.
As to lights, I’ve found the Bi-Xenon HID’s to be superb - esp compared with the old car - even though I’d fitted the hi-power halogens.
As to the rest of it, better performance & MPG, quieter in the cabin, brilliant 825w Meridian hifi, much improved Satnav (shame about the exorbitant upgrade cost!), rear-view camera, keyless starting, heated steering wheel AND heated memory seats (tarty or what!), and (sorry, all) I love the electronic parking brake. OK, I know it is a potential breakdown, but compared with the absolutely cr***y old handbrake, it’s super.
As you may gather, I loved my old HSE, but the Metro is just brilliant.
 I've decided to stop being a good example and will now just be a terrible warning.....
2008 TD4HSE - gone but much loved.
2014MY SD4 Metropolis - very much loved.

I upgraded from Halogens headlamps to Xenon Metropolis headlights. I have also fitted upgraded xenon bulbs D3S. Having gone from candle power halogens I think the xenons are spot on  MY14 Kahn Converted Dynamic - Fuji White Ebony/Pimento Interior
MY15 Xenon Headlight Conversion

MY17 RRS SVR - Estoril Blue Cirrus/Ebony 🪣💺’s

That’s the ‘white’ way to go! Great colour, love my Fuji-white Sd4.
Pics will follow soon - when the hose-pipe system thaws out and I can spruce her up.
Has full LR roof rails and bars, LR sidesteps, tailgate s/steel trim, door cill trims etc., etc. A proper bling-mobile! Looks great with a coat of mud though! I've decided to stop being a good example and will now just be a terrible warning.....
2008 TD4HSE - gone but much loved.
2014MY SD4 Metropolis - very much loved.

There is a single Xenon bulb with dip & main beam controlled by a flap.
I would be checking to see the correct operation of this flap.
My HID's are great, amazing even with a large difference between dip & main beam, both throwing clear white light. Dip has a clear cutoff and mains throwing large amount of light for what seems far into the distance. Dip is so clear you can see the auto-leveling working.
TAZ, there is part number differences between MY13 to MY15 for HID's there could have been changes between the MY's I don't have this information.
Your problem seems like a ballast problem as the voltage/current is controlled by the ballast unit and is matched to the bulb specification of the lamp unit itself so its very important to match bulb specifications with ballast. Your multicolored startup would be caused by the ballast not being able to control the arc discharge. If you find that over extended periods of use that the beam colour seems to be changing then this also points to the ballast. The ballast need to control, basically, a short circuit and as temperature rises the ballast needs to increase current to maintain the arc.
My HID's startup with a bright white flash and settle to a white beam, very little to no blue hue to the light particularly against the LED signature lights which look blue in comparison. MY15
Tyre Pressure Monitoring System (TPMS)
Surround Camera System
InControl Apps soon to be replaced with CarPlay (WIP)
Meridian Premium Surround Sound
Digital Audio Broadcast
Timed Climate
Cruise ECO Data
Follow Me Home Reverse
Extra Features Menu
Picture In Motion
4x4i screen (WIP)
Digital Broadcast TV
Meridian Rear Media with WIFI
Factory Powered Tailgate
Blind Spot Monitoring (BSM)
Reverse Cross Traffic Alert (RCTA)
Electrochromatic Wing Mirrors (WIP)

Thanks for the replies,
I've a service due next month so I'll get them to check out the dip to main flap operation and reflector condition as the dip beam is fine, I'm just not getting the full bright flood of light on main beam for some reason.