Only you can answer that question my friend. I would only pay £120 for the one you describe to use as a plinker with the iron sights, as though good in their day they are not a patch on the modern stuff, and without the old Eley wasps difficult to find one that shoots modern pellets well. On the other hand if its just for the enjoyment of shooting/owning a classic, some people might be willing to pay more. The Vulcan also suffers from splaying breach jaws with prolonged use, which as a collector you are probably aware.
John
Law of any kind only affects those willing to abide by it.