Hi Julian
If the Abbotsbury branch had stayed open for another ten years or so I'm sure that the 14xx would have continued as they were. They remained at Weymouth until the later 1950s when they were transferred away. Six coupled locos were barred from the Abbotsbury branch due to the very sharp curve at Upwey Junction. An Armstrong Goods 0-6-0 working a passenger train was derailed on the curve in 1894 and following investigation as to the cause it was recommended that six coupled locomotives should no longer run on the line. Henceforth four coupled locos were employed, usually of the 517 class with the assistance for a time around the turn of the 20th century by some absorbed 4-4-0 tanks. In due course the 48xx/14xx 0-4-2T worked the line until the passenger service finished. The goods service that continued to run as far as Upwey was worked by the 14xx until they left the district. The remains of the line, having been reduced to a siding from the main line, was no longer covered by the ban on six coupled locos and from then until the goods service finished at the end of 1961 Weymouth pannier tanks was used without apparently any problems.
Hope this is of interest.
Gerry