If you don't know any better then use OEM parts always. You can't go wrong.
OEM filter, sump plug/washer, castrol oil. If you open the manual it will tell you the variant and grade of oil.
I personally use Ester based oils as I've had it explained to me in the past why they are best.
Motul and Fuchs Silkolene both come Ester based and I use the former.
Every forum is sponsored by OpieOils and you can get a discount by mentioning the forum in the sales process.
Get the genuine BMW advantec 5w-40 grade oil. It's quite expensive but it's what bmw use. It's made by shell. BMW used to use the castrol power 1 racing but not anymore, probably for about a year or so now they don't use it. That's across the board with BMW motorrad. You'll get filter from John Clark for ?16 buddy and you can get the shell advantec too. You'll require 3.5 litres, prob best getting 4.
Good luck in your hunt for oils over the counter... Glasgow hasnt any... EK and DALKEITH stock it in litres 16 quid odd... use Opie get our forum discount or ebay 300v - Castrol are safe bets