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Universities tend to offer part-time courses on a heap of subjects, and they can lead to various qualifications, eg a certificate or diploma - (equivalent to first year or second year undergraduate). You can usually dip in and out as well, so taking a course of just 20 credits, for example. So they could be used as samplers, with the bonus that if one samples enough it could build up to a certificate. I had a look on the University of Kent at Canterbury website, and they have a whole list of part-time courses. That might be another thought.
Otherwise therr are usually evening classes advertised around September, in all sorts of interests and levels, - the library could help, perhaps as well with this. Learning something new is always fun, I think, and it's suprising how unexpectedly a major interest can be sparked.