Hi ya and welcome to mini2
Bmw recommend castrol edge 5w30 but be carefully there are a few types just make shore it say it for bmw and meets bmw longlife-04 Halfords | Castrol Edge 5W30 Oil 1 Litre
My local b&q sell it as well cheeper than halfords,
the only thing I would say is it best not to mix oils and always ask when it serviced what they have used.
If you have the last service stamp form the garage that serviced it last give them a ring ask them what they used.
If not the castrol will be fine
Hope this helps