Baseboard Suppliers, not exclusively TT120 of course, but suitable across various scales. Huge thanks to MJ on Hornby Forum for this info

Baseboards…
Model Railway Solutions (MRH)

White Rose Modelworks

Grange and Hodder

DCC Train Automation

GH Modules

Harry Maynard Baseboard modules

Baseboards.co

Model Rail Baseboards (MRB)

Rail Aligners…
Model Tech