My reply turned out to be pretty long. . . I have a lot of favorite beers, but the Best Bitter is my favorite session beer (along with Dry Irish Stout, which gets the exact same commentary below).
This is the hardest part of making English Bitters. A Best Bitter is one of my favorite beers to brew - hitting its peak at about 2-3 months, it's one of the quicker beers I make... and brew day always seems to be spot on for me.
The problem is in the Keezer. I tend to have keezer temps right at 40° (4°C, actually). It's the best compromise, and a great temp for American Pales. . . but you can always warm it up a bit.
The other difficulty is Vol CO2. IMO, English beers are very touchy and I often find it over or under carbonated. I probably need more practice, but it seems as though the carbonation is always perfect just before I kick the keg. I usually leave it at 0 PSI (from the cylinder to the beer) after carbonating it too much...
I may never figure out the cellarmanship of my bitter without buying a cask to serve it from. Luckily, basement temps are perfect for this in the winter.