Composite sink hole saw confused

Hi all, I've never fitted a kitchen and so far have really done well with the base units and worktop. My problem is that I have a composite Cooke & Lewis sink which I need to drill a hole for my new tap. Underneath the sink there is a semi pre-cut type of hole (like cut half way in as a template) and now I need a 32mm hole saw but don't know which 1 to get?. Does it have to be a diamond holesaw?.
Please could someone advise me or link me to the type of product that I need as this would be...

Composite sink hole saw confused