Squeal pulling away

My Octy VRS seems to have developed a Jeckyl and Hyde complex at the moment.

One day it's smooth, fast and handles perfectly. The next it drives like a bag of old bones, handling poorly, labouring to pull away from stationary and with a gear shift like stirring porridge.

I've had a problem with saw toothing previously and have new fronts with the old front tyres switched to the back and the new settings installed. However after 6000 miles the dreaded rumbling seems to be recurring and perhaps this is clouding my judgement on what is happening with the rest of the car.

However, I am convinced that the clutch is occasionally slipping as it sometimes judders as I pull away and at other times it seems to struggle to get the power through to the wheels under acceleration. I have now noticed a squeal sometimes as I let the clutch out when pulling away from stationary.

There's only so many times you can go back to the dealer and if the technician says everthings normal what can you

say? My 16 months of ownership has been occasionally sublime but often frustrating with so many niggles.