Yeah I've personally never had a bad experience customer service-wise with BUK. They have always been excellent - helpful, professional and communicative..... and a watch has never had to go back to anything they've missed or failed to fix. Can't ask for more than that IMO.
Rolex UK and Omega UK have also been superb in my experience. Even Tag (many years ago) was perfectly fine.
IWC UK on the other hand were terrible. My now departed Big Pilot (
) had three trips back to them to sort out it's superfast time gains, and on all three occasions they managed to fix b*gger all! They even managed to scratch the case on the second visit which then required another trip to polish the scratches out! "Fortunately" it was going back again anyway to attempt to fix the timekeeping, so they could kill two birds with one stone. 
Oops, sorry, bit of a negative experience there (in this positive experience thread!), so in true "sh*t sandwich" fashion, I'll end my reiterating that BUK (plus Rolex and Omega) have all been brilliant.