...is it worth buying one for £65 despite it having no bobbin case or pedal?
I'm leaning towards a yes. You will of course have to track down the missing parts and they add a bit to the cost. I guess at least anther £40-50 unless you are lucky. If it's nice looking and perhaps you can test run it with a borrowed pedal, it's within what I would take a chance on (well knowing it might need cleaning and oiling). It might need full rewiring, and it will add to the cost. As long as you are aware of the type of work you take on, there shouldn't be anything stopping you.
I don't know about prices in the UK, but there they tend to go for equivalent of £150 in just a few days. The last one I noticed at that price was complete with case, pedal and I assume bobbin case was there too. They turn up far less frequent around here than UK; one or two a year at most my area.
If you could use a portable machine the Featherweights are nice, but if you want a nice machine to work on at home, a full size machine in a cabinet or table comes off as much more practical. My 201 in a treadle type table, but converted to electric motor and it's a joy to work on.