I've just brewed a St Peter's Ruby kit after seeing it on sale in Lakeland, and having read the reviews. I love a ruby ale, and the St Peter's Ruby kit gets some REALLY good reviews.
I have to say though I haven't found mine to be overly sweet. I fermented for around 10 days, and it's been in bottles for about 3 weeks now. I tried a couple last night and they were starting to taste really good. Lovely ruby colour and crystal clear. Just lacking in body, which I put down to needing a little longer to condition. And not much fizz either to be fair. But very nice nonetheless.
But I digress! As I was saying, I've not really found it to taste sweet at all, which leads me to think you may have had an issue with fermentation? How long did you ferment for? And did you happen to take hydrometer readings before pitching your yeast, and when transferring to the keg?
Also as McMullan asked above, was there any fizz when you poured off your sample? If it came out of the tap amid a surge of hissing and froth then you're on the right lines, and probably just need to give it more time. But if it came out pretty flat and lifeless after 10 days then you may be in trouble.
