I'm not entirely certain of the way that Audi organises build batches, so I'll openly admit up front that this is part-speculation, but I would be quite surprised if Audi builds cars in the exact sequence that they were ORDERED in... -It wouldn't make economic sense for them to do so.
If they did, they'd be spraying different colours one after another... That's just one example. FAR more sensible to organise manufacturing into 'batches', where you make Lava-Grey one day, then a bunch of Black the next... Ibis white as a concerted batch, blue... yellow... etc. -We all know that they charge about 2500 for a custom factory colour order partially because of the need to clean out the old paint colours and load up the new, if they made cars one colour at a time, they'd also have to do this for pretty much EVERY car off the line.
Likewise Open-skye sportbacks versus steel-roof sportbacks... having the glass and operating mechanisms close to the production line but not using them for 70% of the vehicles off the line wouldn't make any sense. -Having it close to the line on days/mornings or shifts where open-skye vehicles are being produced and then having the un-punched roof structures and non-sunroof headliners on shifts when they're NOT building open-skyes makes more sense, and keeps the required parts closer to hand, and production lines tidier.
-Net result, if I ordered TWO differently-specified A3's as factory builds, and signed the contracts for BOTH at the same time... I'd STILL have different build dates. -Now of course, they'd both be within a single 'complete production cycle', and there would naturally be some general similarity in terms of production lead times, but some reasonable variation in lead times is perfectly normal.
This time of year however, ALL auto manufacturers are preparing for the Model-Year production line changeover, and at a certain point the production line will be stopped for re-tooling and reconfiguration. Several manufacturers here in the US are ALSO taking advantage of the pause in production to KEEP the production lines halted for a little longer, in an effort to try and let the glut of unsold cars deplete itself... car sales being down so significantly and all. -It's also allowing them the luxury of a more relaxed deadline for the model-year changeover to be completed if they combine the two, making LOTS more sense than stopping it once for changeover, then starting up again and halting it AGAIN to let the unsold car glut draw down slightly...
So if you happened to order a particular version of the vehicle (Quattro/FWD, Colour, or with a significant structural option like open-skye) for which they had a pretty much fully-subscribed production run BEFORE the mid-year line-halt, you'd be waiting until after the re-start. -If you happened to order a combination for which the production slots were NOT yet fully-subscribed, you could have got a vehicle made BEFORE the line-halt.
Plus, I think the A3 is made in Ingolstadt AND Brussels, -right? -Do all the UK ones come from one or the other, or might they additionally be from different locations?
But post-restart (later model year) vehicles will tend to have higher resale value down the road, as well as perhaps slightly updated touches like radio options etc... depending on whatever the MY changes are this year (I haven't checked) so while the wait for a post-restart car can be agonising, there is a slight reward to waiting.
Keith