I see you are registered in the UK, but you are currently signed in to the US ebay.com site.
Try signing out here and sign back in to the UK site, and try to pay for your purchase there:
https://www.ebay.co.uk/
Some UK users have been having issues with their service providers' Child Safe settings, particularly those using Virgin Media, TalkTalk and Post Office Broadband. If you are using one of those and having problems with pages loading without formatting, try adjusting your Child Safe or Safeguard settings.
"Server down" messages can sometimes be the result of following a bad link, so try to reach the page you want by a different route, if possible.
If you are having problems paying for an item, try going through your Purchase History page, the item page, or your shopping basket.
