I'd say you'd be lucky to get £450 so if you factor in the ludicrous fees with somewhere like ebay you'd be looking at more like £380 net.
The alternative would be trying to sell it on here but you'd likely get a stupid offer as is so often the case with the members market and high value goods.
The S5 will also be dropping pretty quickly, I'm pretty sure it'll be available around £450 in no time pushing the resale value further down.
Basically, get the phone you want, there's no money to be made here that's worth the risk of something going wrong (lost in post/scammer etc).
The alternative would be trying to sell it on here but you'd likely get a stupid offer as is so often the case with the members market and high value goods.
The S5 will also be dropping pretty quickly, I'm pretty sure it'll be available around £450 in no time pushing the resale value further down.
Basically, get the phone you want, there's no money to be made here that's worth the risk of something going wrong (lost in post/scammer etc).