If you do 10k or under per year you should be on a yearly service/oil change. First service is just oil/filter change and a look around the car/checks. The second is the same plus pollen filter.
I was like you with my first service thinking keep it with the main dealership to keep the warranty and get the best px price later on. I paid just over £200 for the first service/inspection.
After a lot of reading on these forum, a message to Audi UK (reply below) I took it to an Audi specialist for my second service, as you can see there is a big difference in price:
2nd service prices:
Cheshire Oaks Audi: £365
Crewe Audi: £401.19
Liverpool Audi: £439.80
'Unit20' who is an Audi specialist
£220.
This is the reply I received from Audi Uk when I asked if I'm OK to use a non main dealership:
As for future PX prices, don't worry as Audi offer the lowest price out there anyway!!! 'We Buy Any Car' are offering me £1,000 more than Audi and that is with me wanting to buy another Audi off them!!!
This weekend I took it to a performance car specialist, he quoted me £1,500 more than Audi just to buy it off me. He also mentioned that as long as the service has been done on time and proof can be shown it doesn't alter the price he'd give me for the car, they all go on CAP prices, so an Audi history wouldn't bump up his offer!
This may be of interest in Glasgow
https://www.pistonheads.com/gassing/topic.asp?t=1251430
Reviews A for Audi
http://www.a4audi.co.uk/testimonials.php