Oxford Rail offer the J27 NER/LNER/BR 0-6-0

[Bigmet]

...You can't rely on any wagon tracking with it's coupling on the centre-line ! ...

Quite. Accurate coupler positioning is a matter of minimising an easily controllable systematic deviation which disturbs the self centering action of pinpoint axle ends and tyre coning. If these self centering actions are allowed to get on with the job with as few perturbations as possible, running is typically fine. (A major surprise in my youthful OO experience was how poor the original wheelsets and bearings of Slater's quite exquisitely moulded wagon kits were. Insufficient self centering action from a miniscule pinpoint and near cylindrical tyre profile.)

[Bigmet]

And a year and a half on, this model continues to perform as well as ever. Still available at a price that most brands moved on from circa 2010. I wouldn't claim that it is perfect - see previous content in this thread - but at the current sub-£100 price it has to be the cheapest good tender model in RTR OO...

The outwardly very similar J26 is advertised as available this year. It will be 'interesting' to see if the price alters, and drags up the asking price of any remaining J27s in stock with it...