over the last few days my iPhone was been freezing up. screen becoming unresponsive
when people phone me I cant accept the call sometimes as I cant slide to accept

I'd suggest trying a restore in iTunes to see if that helps remembering to sync and backup before you do that

If that doesn't help and the phone is under warranty (though it's also worth a go if it isn't) book a genius appointment at your nearest apple store and you should get it swapped if there is a fault