Hello Tom
Thank you for getting back to me.
I’ve tested this in several ways and it works perfectly!
It disables any coupon for the product which has been accepted/countered as an offer and when adding another item to the cart, the item which hasn’t previously had an offer is discounted by the coupon and the offered product isn’t affected.
As everything we sell is one-off jewellery pieces and we have offers set for minimum pricing, this now allows us to accept offers for higher-end items and customers can combine cheaper products with generic discounts.