I would say £80 is fair for one of these. The funny thing is that they turn up on Star Wars cards more often than ESB but command higher prices on SW cards. I guess the Star Wars logo is just more attractive and it is of course the debut card. They do also turn up on Tri Logo and Jedi cards more than ESB in my experience
Here is a link to one that didnt sell at $150 recently. Looks pretty tidy.
I agree with Chris. Many of the first 21 are more common on the SW cardbacks than any of the others....but for some reason first issue commands a higher price. A good example is Original Leia on a Jedi card. Sorry once again.....I went off topic.