Thanks for all the answers... sorry I havent replied; life got hectic 🤯

In the end I contacted custimer services online chat; they gave multiple non-commital reasons it 'could' be and said they would raise it internally

I left it at that thinking I would just have to wait it out...
And then over the next 4 days it slowly started dropping and settled at 6.6% !!!!!

Innnnnnnnteresting! 🤔

Anyway... sorted

Now to investigate some of these "don't need to use promotions" responses above and figure out how the hell I do that!

Thanks!