I always buy Comma G48 antifreeze, you can usually get it cheaper than BMW offer. The Comma stuff is good quality.
https://www.amazon.co.uk/gp/aw/d/B00..._t1_B00G6MX5NK
Is the BMW stuff for £9 pre mixed or concentrated. The link above is for 5 litres of concentrated G48 from a quick Google. If you takes some time looking you can probably get it cheaper elsewhere.
I've always found BMW expensive for consumables, their G48 is the same as the Comma stuff.