[Singh]

I think Neil (Architex) has an office in Swindon so it may be worth asking him, or maybe James (Mkoneman) he is based in Oxford and you want find a fussier guy then him when it comes to paintwork.
I honestly think you had your S4 'mopped' by a bodyshop or amateur valeter and that has put you off having your car polished, if the car is detailed by a professional detailer - there will be no swirls! That is the one of the main points of detailing to remove swirls/defects. These guys are probably more anal (hehe) then any of us are about our own cars. If the one in MK isn't as good a spec, I am guessing it was your second choice for a reason, and if you are still willing to put business the first dealers way, then it would be worth getting a detailer to go and take a look over and give his opinion, the dealer will pay for the detail of course. It is likely to take two days or more. Honestly, I am confident if the detailer says he can get it looking as per your standard, you will be happy, and there will be no swirls.
These guys use a two bucket wash methods with grit guards, wouldn't use a chammy even on a tyre, use a pat drying method so not to inflict any swirls on the paintwork, the dirt is softened and washed away by way of a snow foam before it is even touched with some deep lush sheepskin wash mitt.
We are all looking forward to hearing your thoughts on the D4, get one bought!