Nope, these should be unlocked
I purchased 2 "good" iPhone 7 128gb. One was in awful condition and the other one was in excellent condition so I think its the luck of the draw!
Do you have to stay with Giff Gaff?
Are these phones still under apple warranty (in addition)?
To be fair, if the condition isn't what you expected, you can always just return it. Who knows, some of the 'good' condition ones could easily actually be in excellent condition