If it was in fact a parrot it must have been a kakariki (green with a bit of red/orange colouring on the head. True value about �25, unless it is a colour mutation or handreared one which can go as high as �100.
I am afraid I don't like the chances of getting any recompense. Buying a parrot and then saying after one bought it that it is some other kind of bird is the same as buying a whippet and after you have it home, realise that you bought a poodle. They have obviously been prime candidates for a hoodwinking and, to be perfectly honest, it is their own fault for buying a pet under those conditions.
The police have more important things to do. It can not be proven that an offence has been committed. 24 hours is enough for a healthy bird to deteriorate to the point where it dies. Take the feathers off a bird and you are left with an amazingly small animal. The only recourse you have is to take the seller through the courts yourself which is going to be a costly exercise. And you still have to find this person first. Is it too much to hope that this
http://pets-sale.vivastreet.co.uk/sale-pets+sh effield-s13/kakariki-parakeet3/1831896
was the seller?
lankeela - as above - and others have been warning people on here against exactly the kind of situation as you described when buying a pet. Sorry I can't be more supportive but I am not as diplomatic as others here.