It's going to be 28 cm too big - but if you're on sloping ground you could lose this at the 'high end' of the van - or by sloping out the loose bits at each side and pegging them down a bit further out - the interior draught flaps will prevent any obvious gaps. Our awning is 25cm too big - but we manage perfectly well with it.
If it looks like a dogs dinner when you've got it rigged up(ours doesn't, but awning shape and fit can vary) you can always have it altered - they remove a triangular shaped piece, and restitch it so that you'd never know it had been altered.