You may find the following links useful:
Federation of British Bonsai Societies (FoBBS) http://www.fobbsbonsai.co.uk/
FoBBS Bonsai News http://mailchi.mp/ce69496c1395/fobbs-bonsai-news-issue-21-december-2017-january-87925?e=d0bb77d005
Bonsai Empire https://www.bonsaiempire.com
http://www.colinlewisbonsai.com/Reading.html
For advice on how to grow trees from seed:
https://www.treehelp.com/how-to-grow-a-tree-or-shrub-from-seed/
https://www.forestry.gov.uk/pdf/fcpg018.pdf/$file/fcpg018.pdf
Advice on tying a tree into its pot:
https://bonsaitonight.com/2016/12/27/secure-bonsai-pot/
A beginner’s guide to Bonsai:
https://blog.flowersacrosssydney.com.au/bonsai-for-beginners/