In the end I decided to sort out the interior for the new carriage rather than tackle the stuff under the floor.
And as I have a feeling that there will be more of these design of WHR carriages rolling out of Boston Lodge in the years ahead I've decided to cast the seats this time so I can easily them out as required in future.
I used the same tactic with the FR superbarns last year when I had to make a big batch of the carriages.
However I couldn't use the same master for this one because the WHR carriage seats are slightly bigger and with a simpler seat back design as you can see above.
The way the design of this casting works is to have the table tops cast separately and then glued onto a base which doubles as a spacer to help me position each seat / table combo in place in the carriage.