Wineworks

First timer "Old Timer"

I recently purchased the starter pack and a few other items including an immersion heater as I was not confident of being able to keep the room at a stable temperature. The instructions for the heater stated that it was made for a demijohn with a 1 1/4" dia neck hole, so I cut a 1 1/4" dia hole in the bucket top (quite accurately being a retired engineer) only to find the bung dropped straight through. After blanking off this now unwanted hole I measured the bung and found it needed a 1 1/8" dia hole!!!
Other than that following the instructions for the premiun Cabernet Sauvignon was straight forward, the fermentation took 8 days not the 5/6 mentioned, after racking off to the other container and de-gassing etc I waited another day after adding the last finnings, checked the S.G. again (998) and prepared for bottling, at this point I tasted the wine, it was very sharp and vinigary, not pleasant. I phoned your works for advice and the Lady I spoke to thought that I should go ahead with the bottling and the wine would improve with time. I hope she is right.
Are there any mistakes that a beginner like me might make to cause the wine to be so sharp.
Your service has been first class.
Thank you Michael.