eBay UK customer service, complaints department, seller account, buyer account, feedback contact method. Permanently suspended like me? No reason given?
“You pose a security risk to our marketplace community” but “we can’t provide any further detail to avoid compromising our policies”?
Tell them the impacts on you today!

How would you ideally use ebay? What are they stopping you from doing?
Can you include a monetary impact?
Can you tabulate your time spent finding and using alternatives?

How easy was it to find these addresses?
Do you even have a printer, or did you have to use someone else’s?

How rude were their Customer Service staff to you?
How long were you on the phone before they started talking over you, ignoring your words, and hanging up on you as if you’d been half as insulting as they were?

Were they defamatory or discriminatory? Has this royally fucked up your day for no discernible reason?

Call them now! On… Nevermind! They don’t post their phone number…!

Write them a letter the old-fashioned but legally regulated way: by snail mail!
Include all relevant details, and be as accurate, precise, and non-insulting as possible.

Don’t forget: when you’re done, save the file or take a photo of the paper.
Make sure to remind them every month or year, per your anger levels!

Collectivise your rage! Agitate for justice today!
(Please do not make up shit tho. Legit just include your relevant details, peas and fangs.)

eBay Commerce UK Ltd.
1 More London Place
London, SE1, 2AF, United Kingdom

eBay (UK) Limited
5 New Street Square
London
EC4A 3TW
United Kingdom

Not had a response or resolution yet? Send them a monthly reminder! It’s much harder to ignore physical mail.
Remind them you’re a human being who exists in their shared environment. Fart in their general direction. (But keep the letter placidly inoffensive for best results!)