Some commercial examples of pale ale/bitter you might find:
Samuel Smith's Pale Ale
Bass Ale
Spitfire Ale
Old Speckled Hen
Boddington's British Ale (a poor example IMO. As Budweiser is to Pilsner, Boddington's is to Brit. bitter)
Marstons Pedigree
Bluebird Bitter
Well's Bombadier
recipes: There are some "clone" type bookes out there by Grahm Wheeler and Roger Protz (I think there are three editions of essentially the same book each with a slightly different title, the latest being "Brew Your Own British Real Ale " ) Anyway, the recipes are supoosedly based on informatin gathered directly from the breweries and the author's own brewing experiments.
Many of the recipes are available on line at
http://www.hopandgrain.com/recipes.aspx
There's also a book called 'The Real Ale Almanc" which lists the ingredients and other info for hundreds of british beers. Many of these have been converetd into useable recipes at this site:
http://www.jimsbeerkit.co.uk/forum/viewtopic.php?f=5&t=5022
Alll of this stuff is in metric, but you can convert it easily.
Other good sources of info:
The Barclay Perkins blog as mentioned above
The British Brewer
http://www.britishbrewer.com/ (authentic, tested recipes there too)
http://perfectpint.blogspot.com/2011/02/near-perfect-pint-dark-mild-tasting.html# (recipes and good commentary about them)
One thing you'll notice is that most of the authentic British clone recipes call for sugar in one form or another. The majority of American hombrewers seem to be brainwashed into thinking that the use of sugar in any beer except Belgian stuff is a guarantee of crappy beer, but the various sugars that British brewers have used and continue to use are an important part of the flavor and color profiles of "authentic" british beers. Don't be afriad to use them.
Here's a recipe I came up with to clone Ringwood Fortyniner based on the information in the Real Ale Almanac. It came out pretty tasty and it's simple (and it does NOT use any sugar so the sugar snobs will be happy!):
5 gallons, 70% efficiency
OG - 1.049 - 50
FG - 1.013
IBU - 32-33
Color - 10-11 SRM
8.75lb Maris Otter
6 oz Crystal 120
4 oz Torrified Wheat
1/2 oz Challenger pellets - 60 min
3/4 oz Progress pellets - 60 min
1/4 oz East Kent Goldings - 15 min
Yeast - to be authentic you should use a Ringwood strain, but you could also use any British ale strain you like.
You should vary the amount of the bittering hops depending on their AA% so that you get about 30 IBU's from them with the last 2-3 IBUs comig from the late addition of the EKG