Thanks - that removed the error remotely.
I also ended up downloading MAMP so that I could get the GD extension and test locally also. I'm able to view the form in the browser, but after filling it in and pressing the register button, nothing happens. I don't get any errors or anything and nothing gets inserted into the database.
I've attached a file containing the code. Would you be able to take a look to see what might be happening?
Appreciate your continued support.