The DIY shop is housed in what was, according to old maps, a wagon and wheel works and in the previous post I speculated that, for want of any other information, that the rails might relate to some form of travelling crane. Well I was wrong.
I've now, thanks to issue 190 of the Industrial Railway Record, that the works were the premises of William Gittus & Son Ltd. It appears that in general most of the work involved repairing wagons rather than building new ones, but they had a very distinctive builders plate featuring a dog which they attached to the wagons they worked on.
While it is nice to be able to put a name to the company that ran the works, the article also clears up the issue of the rails...
by 1905 several developments had taken place ... a large wooden building (which could accommodate six wagons and was known to the workmen as the "big shed") was constructed on the west side of the dike. The big shed had a full length traverser at it's west end and was served by four sidings. ... Further expansion took place in the 1920s when extensions were made to the Big Shed and a second similar sized building was erected on its west side. The traverser was then situated between the two shops and two horses were employed to shunt in this area.So we now have a definitive answer, the rails were the remains of the wagon traverser.