sorry Bruders don’t mean to make you feel worse, but there is a pattern there!
basically there is a container of frames from Taiwan on a boat somewhere. It may come to the UK it may go somewhere else. (I was looking to get a Trance and the shop told me because Trance was doing well in the UK a shipment bound elsewhere may get diverted to the UK. So presumably the opposite can happen).
It sounds to me though like you have already accepted the move from week 13 to week 16.
Go speak to the shop in person. You say they are OK folks, bike shop owners aren’t villains. (Or more accurately villains don’t run bike shops because other forms of villainy are more profitable!)
The shop probably feel bad about messing you around too, tho likely there is nothing they can do about it.
Don’t accept a substitute unless you want the substitute.