http://www.besbrodepianos.co.uk/pianose ... kinson.htm
which puts your piano in the late 1870s, so Gill the Piano was very much correct with the date.
Whether or not it is worth restoring is very much up to yourself and how much money you wish to spend on it. Is this piano loved because of its looks, or the way it plays, or that people just like to play it even though you think it needs restoring ? I am not a tuner or piano technician so can only advise from the point of view of being an amateur pianist. Unfortunately your photographs do not show the piano frame which would show the string damping mechanism and whether or not it is straight strung. Has the piano been tuned and does it stay in tune for a number of months ? As a pianist I like the sound and touch of a modern piano and that is how I would invest my money, but of course that is a personal choice.
If the piano is loved because of its looks, one method of restoring it may be to have the frame, strings and keys stripped out and the internals replaced with an electronic piano. Vale Pianos ( https://valepianos.co.uk) in Worcestershire do this conversion but the piano has to be wide enough to accommodate a 88 note keyboard.
Edit. A more careful look at the photographs does indicate it is straight strung and I suspect given the age it is over damped (meaning the string damping is not particularly good for the higher notes). Therefore wouldn't personally consider restoration as an acoustic piano but if I wanted to keep the original case I would enquire about electronic piano conversion, expecting a £2000-£3000 bill at the end of the process.
I will see what I can find on William Hague. If you want to search inside the piano for clues, have a look at
For general information, see
1886 Not listed.
1894 Kelly's Directory; Pianoforte Makers & Warehouses include William Haigh, 34 Town Hall Street, Sowerby Bridge.
1899 Kelly's Directory; Pianoforte Makers & Warehouses include William Haigh, 34 Town Hall Street, Sowerby Bridge & 13 Wainhouse Road, Halifax.
1911 Kelly's Directory; Pianoforte Makers & Warehouses include William Haigh, 34 Town Hall Street, Sowerby Bridge.
1914 Music Trades Directory; William Haigh, 34 Town Hall Street, Sowerby Bridge, Pianos &c.
1928 Not listed.
1938 Not listed.