I'm glad this is being asked - I wanted to post a similar question. From what I have seen others say (but I have not verified this myself in the T&Cs), it seems 100% free for the seller here in the UK if the item sells to another address in the UK. If it sells to the US for example, then fees apply as normal.
The next bit is that it is only free when then total combined account sales stay under £1,500 in a year (unsure if that's calendar year, or rolling 365 day period). If you go over that amount then you must enroll as a business seller to continue (you start paying fees) and also HMRC are now notified of your extra income that I presume will attract personal tax.
I am looking to sell a couple high end pieces very soon, so I am seriously considering selling on eBay again. I have not sold anything on eBay since they dropped PayPal and pay into a bank account so yet to experience that part. All considered, it looks like a good deal if you can stay under £1,500 in sales. And like it or not, great to see eBay trying new things to stay relevant. I'll be giving it a go with something small to start with!
Cheers, Jared.