replace iPhone help!

[jellyjiggles]

If I buy an unlocked iPhone in eBay can I just put my Sim in and remain on the same sim only contract?

If not what's the cheapest way for me to replace my 5year old dying iPhone when money is tight?!

I'm open to not having an iPhone but as I've neither an iPad or iPod we use my phone as both.

Don't know what the best thing to do is!

Theoretically yes. Make sure it uses the same size sim, or you'll need to get a new one and transfer the number over.
Do watch out when buying used that it hasn't been reported stolen to an insurance company. If that has happened, it can be blocked remotely, and you will not be able to use it. I'm not sure how you get round that if buying a used one, other than buying from one of the networks' refurb outlets.

Really the only difference between an iphone and any other decent smartphone is itunes. If you are wedded to that, you may as well stick with it, if not, get the best phone you can for the budget you've got.

Thank you. Decided to go with a Huawei instead. Looks to be a really decent phone for less £