[Ravenser]

Peter:

You may want to take a look at the Pullmans. They're essentially accurate and the type is more appropriate for ECML Pullman trains than the current Hornby Pullmans . I think Tony Wright covers upgrades for them in one of the BRM DVDs

The TTAs can produce a good result with work and some A1 etches but I suspect they're a bit late for your tastes

 

[Ravenser]

As far as the TTA tanks are concerned, there is effectively a detailing kit on the market already as A1 Models have offered a replacement etched walkway/ladder in 2 versions for a number of years - supplies of A1 stuff can be erratic but think rthese items are still out there. On the couple I've done, underframe detailing mainly involved carving away bits that should not really be there. These days even rewheeling should be unnecessary