I have an old iPhone 3G, Cex offers £150, I see prices eBay prices from £120 - £150, i'd probably get £120 as I am a newbie then there is the hassle of the Paypal hold etc, any other recommendations? And can you actually trust these sites that buy your mobiles?

If CEX is offering prices at the top end of the eBay prices you see (unlikely) then go for CEX! Generally eBay gets the highest prices - higher than the likes of mazuma etc.

My iPhone is unlocked, alot of these sites don't care and are offering £80 or so, CEX are offering almost double that for an unlocked grade B, sounds to good to be true, might take it into a store tomorrow

these sites are rip off merchants.

If you don't want hassle you probably want a quick fix but if you change your mind i would look to sell it on ebay etc for a more reasonable price.

RPC Recycle offered me almost £30 more than any other 'buy your mobile site', was easy enough too. It took 5 days from ordering the jiffy bag to having the money in the bank. You'd probably get more for your phone if you sold privatly, AdTrader and Gumtree are a good place to try, no fees either!

CEX generally do offer good prices for phones (but then resell them for rip off prices). I recently sold a blackberry curve privately and only got a few quid more, after factoring in P&P, than CEX would have paid me for it

Just watch out as CEX will downgrade the class of the phone from A to B or so on for pretty much anything. They also wouldn't take a iPhone from us a few months back as the dock cable's insulating plastic was coming away from the plug a bit (still worked fine mind)

Yes I had noticed they do seem to resell them at rip of prices, by the time I take eBay fees into account which would be around £20 at least CEX works out the best.