Swollen battery

On Saturday I discovered the battery had swollen in my iPad air 2 and caused the joint to separate on on side of the iPad between the front and back screen.

I took it to an appointment at the stormfront store in Stirling and they advised me all they could do was replace the full iPad at a cost of £279 as it is out of warranty and on an iPad it is not possible to change just the battery as the iPad cannot be opened.

After leaving the store I checked the apple website and it states for battery services the full iPad is replaced at the battery exchange cost £89. I returned to the store and asked the same member of staff about it and he advised me that he knew about it but didn't think that they could offer it as an apple authorised service provider, that it was only a service at Apple stores...

Has anyone experienced a swollen battery with the iPad and what was apple's response?