I've been curating a list of UK resources for my own use:
https://stormleather.com/ - Leather
https://identityleathercraft.com/ - Leather, supplies, events, workshops
https://www.jwoodleathers.co.uk/ - Leather
https://www.leathermerchantsussex.co.uk/ - Leather
https://www.jhleather.co.uk/ - Workshops, tutorials
https://www.ebay.co.uk/str/littlebearco - Supplies
https://www.hedgehogleather.co.uk/ - Leather, supplies
https://leather4craft.co.uk/ - Leather, supplies, workshops
https://www.georgebarnsleyandsons.co.uk/ - Toolmaker
https://armitageleather.com/ - Workshops, info