Well, I authorised Barletts to go ahead with the replacement headlight, and asked for it to be done at the same time as fitting the tyres and geometry. However, they rang back later to say the headlights are not in stock anywhere in the UK, and are on back order from Germany, so could be a couple of weeks or longer to wait...... Gutted.
On a more positive note, I received 2 letters from DVLA this morning. One was my shiny new driving licence, and the other was my V5C, so at least that is something that's gone right, ha ha!