I seem to have a bit of a dilemma with my application for voluntary work?

I need to find at least a few weeks voluntary work in a Dentistry clinic over the summer. The dilemma is that I have no GCSE results at the moment and my predicted grades are low - mainly C's, but I've got nothing below a B grade in my GCSE exams as of yet - so my predicted grades aren't a true reflection of my real academic ability. It's vital that I get a placement, but I doubt I'll get a placement with my predicted grades, should I send a letter of application for the time being or just leave out the predicted grades part on my CV?