i think that you will find that condition is probably more important, unless models are ultra rare. I am not sure that there is a great collectors market in the UK, more enthusiasts that refurbish and use the saws.
Of the ones to highlight, and probably not car boot are things like brass backed back saws. The easiest thing would be to take a picture of them all laid out, and somebody will soon be able to tell you what is "interesting" or worth a closer look.
Disstons saws are rated highly, as are many others, but if the teeth are all over the place and they need a lot of work, it often isnt worth the effort, because a better one will be available at a reasonable price elsewhere.
