I'm getting one soon and my hair dresser said it would be about 50-60 pounds I can't wait! Make sure you know wht kind of curls you want and try to imagin what it would look like on you lol but if you have short hair it would make it look even shorter and that probably would look really weird :S any ways make sure you choose a one that would best suit you because down the line and you don't like it, it would be a waste of money :D
If you want a high worthit perm it would have to be about £70-£60 pound!
A good idea is to buy some cheap tongs (Argos have a set for about 5 pounds) or buy a set of bendy rollers (Boots or Superdrug) and practice curling your hair to see if you like the finished effect. Try it several times in the style you'll get and get some opinions of whether it suits you or not. Also when you go for it, take a photo along of your ideal hairstyle so the stylist has something to work from. There are lots of hairstyle websites out there where you can filter long/short hair for inspiration. Or look for celebs on google images for ideas.
A good perm should cost around £60 but it could be higher or lower depending on the effect you want
You have to be careful when getting a perm, make sure its something you desperately want...