…for the time being.
For some reason all tweets to 86444 are appearing multiple times in the timeline. Each message has a unique tweet id, and as the Vodafone traffic is only showing one message the fault must be with Twitter (the same issue is happening with a Canadian shortcode 21212)
As I do all my tweeting via the browser on my phone I can’t confirm this, however I believe sending tweets to the UK long number +447624801423 won’t result in duplicate tweets.