I'm not trying to be inflammatory but you can't really make me believe that most enthusiasts prefer riding behind some strangely coloured industrial saddle tank to, say, a proper mainline loco (even a smaller type like an 41XXX Ivatt or BR Standard tank). The Austerity tanks have their place in preservation (compact, reasonably powerful and were cheaply available during the genesis of the preservation movement) but I wouldn't be particularly thrilled to visit a preserved line where that was the only motive power for the day. Yet I was quite happy to ride up and down behind the Ivatt at the KWVR last year when it was the only thing running (mid week visit). The Ivatt evoked romantic thoughts of Waterloo and the SR branches in the 60's, whereas an Austerity is just a shunter to me, however competent they may be.