A few years ago when I used to watch my listings I would notice similar activity. Now I just "list em and forget em". I really couldn't tell ya anymore. I'd check it again in about 12 hours and if it's still not there then I would be more concerned.
Your listing was flagged and is now being reviewed by trust and safety. If your item is generic and your listing did not violate eBay any policies it will appear after a few hours.
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"i once met face to face with a shadow being" stanislav
Not sure about the UK but even established U.S. accounts it can take hours of off and on listings to show up on the site. Obviously the better reputation you have established with eBay the less of the problem this becomes.