The value of the Boley lathe will be in the accessories that are included with it. The same goes for the Unimat.
What is shown in the picture has a low value because you cannot do anything useful with it.
It would only be bought as spare parts by someone who already has one and wants the lever-operated tailstock and lever-operated slide. If you can find the collets, that would add at least 50% to what you would sell it for.
It would be good to browse the lathes.co.uk pages for the Boley make and then search around for anything and everything that looks as if it belongs to or with the lathe.