Sounds like another candidate for the walk away club.
You need to fill in the easy online form to CMA regarding abolishing couriers of our choice in favour of eBay’s choice, which is illegal for competition in the UK.
EBay are an absolute disgrace that don’t care one bit for loyal members who got them to this position over the years. They have stuck 2 fingers up to all of us but are still laughing all the way to the bank for the way they have screwed us all over. They need to be taught this isn’t on and the CMA will get involved if everyone complains AND stops using eBay