If I brought a phone locked onto iTunes screen could I fix it and use it by restoring from my iTunes or not

Try it.

If you need to enter the password for Find My iPhone then you cannot use it until the previous owner unlock it.

Megz19uk wrote:

IIt's not been reset I've found out, so if it has find my iPhone enabled is it basically useless, no way around it

thanks

That's correct. Ask for refund.

You are welcome.

Read what the seller needs to do before you buy below:

What to do before selling or giving away your iPhone, iPad, or iPod touch - Apple Support