You could always back sweeten with a little honey. I had a batch a while ago which turned out like that (turns out I'd used too much yeast by mistake), but after the extra honey, it came out delicious! Obviously campden and potassium sorbate too ;-)
mmm, maybe could be the extra yeast dose... I put in 2 7g packets... Could it be due of that?
About the backsweeting, how much honey/sugar should I add to get something edible?