Iphone 4 8gb how much should i expect for a trade in?

How much would i expect to trade this in its got box ect 3 months old

I'd say if you put it on ebay £100-150

There's always envirofone, an iPhone 4 8gb is worth £87 however I expect you could get a lot more money for it elsewhere, don't trade it in to a phone store you won't get a penny for it they are very stingey.
Look at this URL for a selection of selling prices from trusted websites.
http://mobilevaluer.com/mobile/working/apple/iphone-4-8gb/