The workshop notes can be downloaded here
Some useful online conifer resources
https://www.arboretumwespelaar.be/EN/Identification_keys_and_illustrations/Identification_keys There’s also a good image gallery which is worth looking at.
https://conifers.fscbiodiversity.uk/ is a work in progress, so please send Matt any feedback you can.
https://www.conifers.org/ An extensive resource, though without identification keys.
http://www.theplantlist.org/ A useful place to check synonyms and currently accepted names of all plants, not just conifers.
Some useful books
Trees of Britain and Northern Europe. Alan Mitchell. 2001
Conifers in the British Isles. A descriptive handbook. 1972
Trees (Eyewitness Handbooks). Alan J Combes. 1992
Trees of Britain and Europe. Keith Rushforth. 1999
A Handbook of Coniferae and Ginkgoaceae. Dallimore and Jackson. 1966
A Natural History of Conifers. Aljos Farjon. 2008