Only eBay can remove a seller from their site who is still in recent transactions. They must have breached some selling regulations for eBay to do this.
If a reasonable time has passed your item's last estimated date for delivery and seller has been removed, you need to contact eBay Customer Services for them to open a case, to refund you.
This is the easiest and quickest way to contact eBay Customer Services, for a Call Back option.
https://www.ebay.co.uk/help/eua?id=5275&mkevt=1&mkpid
Lines open 8 a.m. - 10 p.m. on weekdays
9 a.m. - 6 p.m. on weekends.
Automated agents will be available on chat outside of the above hours.
I recommend contacting CS first thing in the morning as there's more chance of Dublin answering.
@cavolo111