In the manual for the Samsung Galaxy S3 phone (that I should be receiving in the next few days) it says that pressing the Power button will do that, and I wouldn't be surprised if that is how it works for other Samsung phones.
You could try googling for the manual for your particular model, which is what I did to get mine.
its a samsung s5260 i wont invest in anything over £50 due to the amounts of phones i've gone through.
in the settings it doesn't offer a swipe lock just a phone lock which ive applied and is incredibly annoying as it is now like fought knox too do anything.
am also worried about blocking the phone if it decides to do what i said in my OP.
someone told me about an app,i tried searching but found nothing.
i think ill go back to orange shop but i cant find the receipt is a bank statement showing purchase enough?