Hi, I've a 12 plate 2011 Ford focus titanium x tdci 1.6 

Both headlights are cloudy and pretty much knackered. They are xenon headlights with the turning lights etc and I've been told that just replacing the whole headlight units will cause fault alarms in the car. 

Anyone know anything about this? 

I'm not fussed about them being xenon lights. I'd be happy to whack some cheap halogen headlamps in. Can I do this? 

Would it need mapping or new wiring loom? 

I just want to get the car through its mot and on the road as cheap as possible please

On a 2008 ST, I had to replace both units (HIDs had lost beam due to blackening of the refectors).  Very expensive and I did need the levelling reset.  I expect yours will certainly need some mapping, even with HID replacements.

Bring back H4s! Only about a Lady Godiva.

I put new lamps on my 2010 ST some years back - what needed to be reset with the levelling? I just manually adjusted mine to match the beam kick points of the old lamps, though there wasn’t much left to see they were that bad 

Not sure what it actually did to the self levelling, but was recommended to do it by the independent Ford Specialist I use.

Personally having four cars with three of them having H4s, and just the Focus with the HID/Xenon, brighter does not mean better, either when you are in front or behind the lamp !