Most local auction rooms are happy to give free valuations (because, obviously they hope that you'll sell through them).
You could always look for something similar on e-bay but check that the price shown is as the result of genuine bid and not just an optimistic figure quoted as a starting point by the vendor.
I've done quite a bit of buying and selling at auction over the years. While I've never really dealt in toys I do know that condition is all important. e.g. a die-cast metal toy in mint condition in it's original box (also in mint condition) might sell for, say, �200. If the toy is just as good but the box is a bit tatty , the price might drop to �120. Remove the box, but with the toy still in mint condition could take the price down to �50. A few light scuffs on the toy could drop the price to �15. If the toy is in the usual, 'well played with' state, you might get �5 from someone who needs it for their collection, otherwise it's only worth �1. Same toy - vastly different prices!
Chris