Thanks for your help! That's it :)

I can't tell from your photos, but the most common kind of bedding Impatiens (I. walleriana) is effected by a fungal disease, downy mildew, in the US, and it has at least been present in the UK according to this article. You may find other articles about downy mildew that tell you more about how much of a problem it currently might be for you, but it isn't recommended here in many parts of the US last I checked. Happily, New Guinea impatiens, Impatiens × hawkeri, isn't bothered by it. It has similar flowers and is more sun tolerant.

Yeah, definitely a Callistemon, but as to the species and cultivar I can't say.

This is emerging Monarda. Do you think that the stems on these would be as thin, and as dark purple as the OP's plant when they grow another inch or two, like in the photo? Cunila oreganoides is also a mint so if you're going to do a smell test to tell the two species apart what smell will you be looking for? Well, Monarda smells minty with a spicy note and Cunila has a very sweet pleasant, strong minty smell. If you have already smelled Monarda , you should notice the difference. Cunila blooms in autumn after all the Monarda species are finished blooming. Yes, we should wait and see. https://www.google.com/search?q=cunila+origanoides+leaf&tbm=isch&ved=2ahUKEwjox-SW8e3vAhUMYawKHf9mDsYQ2-cCegQIABAC&oq=cunila+origanoides+leaf&gs_lcp=ChJtb2JpbGUtZ3dzLXdpei1pbWcQAzIECCMQJzoECAAQGDoECAAQHlDWtAFYtcsBYJDTAWgAcAB4AIABrwGIAYUGkgEDMS41mAEAoAEBwAEB&sclient=mobile-gws-wiz-img&ei=ZpBuYOj8AozCsQX_zbmwDA&bih=563&biw=320&client=ms-android-verizon&prmd=mivn