Thanks for this David. Yes I have spelt Tomkison wrongly - more haste less speed! I did consult your videos regarding the Clayson and Garrett which were extremely helpful. In fact there was a somewhat similar repair to execute to the hitch pin rails together with a crack and some warping in the soundboard which went back into place once the hitch pin rails were dealt with and has been very successfully reglued after taking time to manufacture an accurate jig to hold it in place during the drying process-in fact the former crack is now unnoticeable and has not re-appeared (so far) as the strings are brought back into tune and the instrument is now suitably resonant. It was possible to do all this without removing strings, merely loosening them and moving them aside as you did but I did spend some time contemplating and preparing for the project first which was worth it.
I'm now doing tuning and regulation but will then repolish the case as far as is necessary and bring the instrument into use. I have to say that I have been very excited and inspired with this project, particularly as the instrument is well engineered and worth the effort.
I have obtained hinge leather for square pianos from Lucy Coad who also sells vellum for the dampers. Its possible to get vegetable tanned goatskin which is hard enough to recover the hammers from Russell's Leather. You will know that Malcolm Rose at Lewes sells authentic iron and brass strings. not the covered strings though, which seem rather expensive.The daunting bit is removing the old hinge leather without taking too much wood away so that the new leather will glue firmly in place of the old with animal glue. I am researching the availability of very narrow fretsaw blades for this. You may know there is a web site Friends of Square Pianos www.friendsofsquarepianos.co.uk/
which I have joined which is very helpful. They are trying to record all extant Tomkison pianos and would be very interested in yours. They dated mine almost instantly and gave some interesting possible provenance for it. They have a link which gives a source of supply for early instrument cloth (like felt) which is a very useful product.
Apart from somewhat extensive musical actrivities I also repair and restore antique wooden furniture which is a good starting point for all this, but like everybody else money is short at the moment so I would not be able to do much on a pro bono basis unless times improve. I'd be happy to have a look though, and comment at some stage if that would be helpful.