post Uttoxeter Sprint 2024 issues

A place to put issues that came out of the Uttoxeter Sprint.

Immediate:

• #43 (closed) restructure variables files (and improve their documentation)
• test and merge into a branch Thames
• bridge Thames custom CSS into core where sensible
• bridge Wellow custom CSS into core where sensible
• test and adapt basic customiser PR to offer basic font-size customisation (& possible key colour)
• latest sub-issues from #5 (closed)
• #45 (closed) - inline flex
• Discuss #44 (on call)
• Any others added below