My iPhone 4 has run out of warranty, can I get a new replacement?

I have an iPhone 4, i'm on pay as you go and I do not have insurance. I also have no warranty as I got my iphone as soon as it came out (so it's definetely more than 1 year old) I have noticed my lock button sometimes stops working and It's really annoying. I wondered if I could take my phone to an apple store and tell them about my problems and if they could get me a brand new replacement, I'm not sure if they would give me a new one though as I have no insurance or warranty. Does this matter?

No.
You need to buy a new one.

Of course not.
you need a warranty.
you wil need to pay $199 to fix the home button.

Apple warrenty dosent cover much any way and the lock button only cost like 5£ on ebay so no big deal take it to a repair shop and see how much they charge