Look to see if there are any of these "hackathons" in your area, if you're interested - they're basically group programming events where do team based programming challenges and stuff, although the actual content seems to vary widely. Despite the name, they don't necessarily have anything to do with hacking or cybersecurity.
You could do some raspberry pi stuff - it's possible you could arrange something via your school, I think there are some schemes where your school can get them for free/considerably less than retail through educational outreach things, for clubs and so on.
Beyond extracurricular stuff (which isn't that important anyway), in terms of university degrees to consider - Edinburgh have a Cognitive Science course, which has pretty varied course content and can be tailored a lot by the looks of it, but involves various interdisciplinary and crossdisicplinary content in psychology, computing, linguistics and philosophy. Although I don't know the extent of any possible overlap, Goldsmiths' offers CS and has a reasonably well regarded Psychology department you may be able to take modules in.
At Cambridge you can take Psychology in the first year of the Computer Science tripos, you can take two CS papers in the Psychological and Behavioural Science tripos, and you can take 1 CS paper (and two maths papers) in the Natural Science tripos (which has options for specialising in Psychology and/or Neuroscience). I also believe you can pursue Psychology in Natural Sciences at Durham as well (which I know offers CS as an option)
On the more mathematical side, Warwick has the aforementioned Data Science course as well as their Discrete Mathematics course (which is something of a joint honours CS/Maths course, focusing on the relevant areas of discrete mathematics and theoretical CS) and UCL has it's Mathematical Computation course. While in some senses there are joint honours courses, they are slightly more interdisciplinary than multidisciplinary.