However one looks at this, a pre group CLC layout will be difficult to populate with stock except freight wise.
Scratch building is pretty much your only option for coaching stock.
There are locomotives to build in Judith Edges N5 and if you are lucky, you might turn up an auld white whitemetal beast.
I was lucky enough to have operated Andy Gibbs' Whetstone on a couple of occasions and that was a pure GC London extension layout. It took a good deal of scratch building and butchery produced the stock from various sources frae memory. I also was part of the Plemsworth team, a layout which was CLC post grouping, circa 1929. Locomotives used were mainly ex GC but again, limited by what was available. No genuine CLC coaching stock was ever built as none of us were coach builders.
Bill Bedford did do some CLC stock, as built by the GNR pre WW1. Those etched now seem unavailable.