I recently had my 335D serviced by Sytner, it's 3rd oil service so the air filter, oil filter, microfilter, oil change, brake fluid top up and what not needed doing and mine is also fairly low for it's age, 50k mileage for a 7-8yr old car.
I got some discount by:
1. Supplying my own oil (8ltrs from ECP)
2. Haggling (rang around many places) and;
3. Buying all my replacement parts off Cotswold BMW (bmwland.co.uk) as any member gets a small but worthy discount of any BMW part
What I can remember is that all the parts (includeing delivery and discount) came to about £140. The labour charged by Sytner was about £136 inc VAT!! It was by far the BEST price I was getting. Even my local indy was in that same region price wise, with the next best price tag of £450 from main BMW Dealer (for parts and labour)
Worth holding out and haggling and if the OBC says to replace, get it replaced. If not, I'd still do it for peace of mind given you're getting the oil changed and it's the 3rd oil service. It'll only save you labour down the line.
Best of luck.
Now: E92 335D
Gone But Not Forgotten: E90 320D Alpine White