The "my beer tastes sour" issue is difficult as an early off flavor may not indicate a problem. If I were in the neighborhood, my first inclination would be to get a taste of the beer before diagnosing. I wish I could visit you in the U.K. (as I did a semester abroad there and it was brilliant), but alas its not in the cards.
Here are my concerns:
1) It sounds like the beer is relatively young for such a heavy beer. It would be helpful to know the timeframe from the initial brew, to the primary/secondary and to "barreling" (I assume you mean kegging, or at least know what you mean by barreling). If you have a link to the recipe, product you bought or a description that might help.
2) the "sour" description is always curious. Could you be more descriptive about the specific flavor, i.e. is it sharp, acidic, or drying, is the mouthfeel funny (like slick), is the beer cloudy, is the beer overcarbonated, or is the sour flavor tart (might indicate a lactobacillus infection), a bit cheese-like, or something else?
3) If it were sour as you said, and considering your verbage, "its getting hard to drink" leads me to believe that you have a contaminant in your beer. The human palate is remarkable in the ability to detect spoilants. The difficulty to swallow can precede flavor or odor detection of a spoilant". In my experience the most common is wild-yeast infection (the airborne kind that lives in houselholds).
If the beer is young, give it a month in cool storage (unless by barreling you meant serving real ale style and it has been exposed to the air). If it is contaminated, you'll have more evidence. If not, it may very well taste better.
Finally, consider purchasing the book "How to Brew" by John Palmer or at the very least visit his website at www.howtobrew.com
. Most off all, keep learning and keep brewing!