Treat it like a red wine. Cellar temperature. That goes for most big ales.
Pouring a beer always depends on the beer itself and how fizzy it is. The average barley wine will be pretty low in carbonation, perhaps even flat so I would pour it straight.
My rule of thumb is to always tilt the glass at first and if it looks okay, then move to straight but it all depends.
Edit: Just noticed TBN got there before me while I was looking at another tab.
As promised here are my thoughts on the O'Hara's barrel aged barley wine:
Poors very flat with no head to speak of.
There are very little aromas either, perhaps a little hint of the spirits from the barrel aging.
Flavourwise it is also very disappointint. The only dominant flavour is the alcohol. There is perhaps a hint of biscuity maltyness there, but nothing much to speak of.
To be honest, for a beer that has such a high ABV I was expecting something much more complex and interesting.
I was hoping for something along the lines of Eight Degrees Zeus double IPA or the more recent My Name Is Vladimir from Brewdog.
I appreciate that this is a barley wine and not an IPA, but even so, it just doesn't deliver anything even remotely interesting to me.
The two other guys with me on the night were more or less of the same opinion. Suffice it to say the bottle didn't even get finished.
I also wasn't impressed with O'Hara's double IPA, so maybe its just O'Hara's and me don't get on ... or perhaps my expectations for what a barley wine should deliver was wide of the mark?
Since the beer itself had no great depth of flavour it had no problem matching the dessert ... I doubt it would clash with anything!
With a price tab of 12.99 euro this was definitely money not well spent.