I generally find Innis and Gunn's "oakiness" to be pretty consistent but I just tried the 750ml version (which is available at Tesco now) and it's CONSIDERABLY more oaky than the Innis and Gunn I'm used to.
I'm a huge fan of the American oak flavours (my favorite wines always end up being heavily oaked big Reds or super buttery California Chardonnays, too; so I REALLY like oak(and apparently diacetyl in the case of many of the California Chardonnays)) and Innis and Gunn normally isn't this oaky; supposedly they use a "marrying vat" which should ensure consistency but this 750ml version is considerably more oaky than normal. (I like it more than the limited edition rum cask aged-version.)
-Their limited run IPA is pretty nice, too although the one that I had was a little bit skunky, it worked with the oak backing it up.
I hope this isn't just the 750ml version, I hope Innis and Gunn is just cranking up the oak dial. (I was suprised to find out that they're the #1 most popular British beer in Canada now, and the 2nd most popular in Sweden.) -Disclaimer: According to Wikipedia so take that with a grain of salt.
Long story, made short: If you LIKE oak flavors, grab the 750ml Innis and Gunn at Tesco.
Adam