Sounds like a typical 'fobbing off' job. Tennnis is crazy. Have you got a recent x-ray to show us? The NHS love the old rest it in a collar and cuff sling and it will be alright. That is, you'll be left with a permanently non-united fracture. As 16 I would say a fixation is almost more beneficial than in an older patient who may not be wanting to pursue overhead activities (although that does include sleeping!).

Where in the UK are you based?