You'll need to contact Customer Services again, but I recommend trying only very first thing in the morning when the lines first open at 8 a.m. on weekdays and 9 a.m. on weekend, there's more chance of Dublin answering , and perhaps understanding a little more, about postcodes in the UK.
Only speak to them, it's a call back option, so you'll hear if it's the dulcet tones from the Emerald Isles !
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.
@brewa_3490