Hi Stuart, I bought a new OE front roundel for my E86 on Amazon last year for just over £40. I think you can get 70mm stickers for them but as the roundels are curved I wasn't too sure how well a sticker would fit. Luckily I haven't had issues with the other badges.
As for wheel centre caps you need 68mm ones. You can get them on Ebay and Amazon for £5/6 a set but although they may have BMW stamped on the back they obviously aren't OE parts! I got a couple of sets in 2018 but haven't used them yet as I sold the car and the wheels, but based on what I had read on here I got ones with 10 clips as they are supposed to fit better. And while it seems they may only last a couple of years, at that price they're just consumables!
Gear knob wise you can get a genuine 5 speed ZHP from Cotswold BMW or Sopers of Lincoln for around £50 as they both give a forum discount. I think it's actually an E46 Sport part.
Or you can get something that looks similar but won't be as heavy from aliexpress for £10-15 - depends if you are looking for OE or just an improvement within a budget.
This alieexpress one cost me about £13 a couple of years ago.