Sorry, I do not know, but would a second hand set of working winches (of more modern design - say £50 for a pair) on eBay or the like be more practical or make more financial sense?
Not knowing the price of springs, I could be talking rubbish.
They look like Gibb bottom action winches. The chances of getting new springs is slim. You may need to get some piano wire of the correct diameter and make your own.
Sorry i can't help with the exact model, but a quick search shows that some Barton winches had those vertical inserts.... and indeed, some of their current 'snubber' winches still do..
One currently on eBay even appears to have the bottom slot for the handle. On second thoughts, it's on the top.