There are many suppliers of bees all over the UK, it just depends what kind of bee's you'd like. We would recommend sourcing bees locally from a reputable seller where possible.
If you're struggling to find a local supplier for bees we can recommend Black Mountain Honey.
They are a family run, commercial bee farming business based in Wales. They produce honey, bees, nucs, queens and Laurence has a YouTube channel with beekeeping tips, tutorials and product reviews.