how do i find the part number for my car, its either 280ml or 288ml, phoned audi, they will not tell me the part number unless i purchase?

Yes we know Audi won’t Charles , and you can’t really blame them. 
Where have you enquired to buy aftermarket discs and pads, and what brand are you looking for? 
Kind regards,

Gareth. 

Hi Gareth, Ive bought through Larkspeed, very helpful and informative and competitevly priced. EBC Greenstuff pads and entery level disks. ML performance gave me the wrong part and ended up waisting a lot of time and energy.

Thanks

Charles

Thanks Charles,

Try LLL Parts where you may find original part numbers.

In case it helps, I use Parts in Motion (Exeter) who have always given me superb service and very competitive prices on discs etc. 

Kind regards,

Gareth.