For a 5g batch of ESB, I start with about 10.5 lbs Maris Otter, and 1/2 lb English Crystal 55. Most times, those are the only fermentables I use. I mash with 1 qt water per lb grain for 90 minutes at 150F. For hops, I use about 1 oz Norther Brewer for bittering, an oz of some sort of Goldings for flavour at 15 minutes, and another oz of Goldings for aroma at flame-out..
I get an OG of about 1.062, and an FG of about 1.012. Colour is about 8 SRM, and about 45 IBU's with no citrus.
I treat my water to give 100 - 150 ppm Calcium, 200 - 250 ppm Sulfate, and about 20 ppm Chloride.
From that basic recipe, there are a lot of slight variations to adjust the brew.
If I want it darker, I'll add about 4 oz dark crystal or possibly a very small amount of chocolate malt.
If I want to dry it out a bit, I would add about 1/2 lb sugar to the boil.
If I want to increase the mouth feel, I may add 1/2 lb torrified wheat.
If I want something a little less malty, I would add 1/2 - 1 lb of flaked corn.
If I want to reduce the hop presence a bit, I'd reduce the two late hop additions by 1/4 oz.
I must admit that when I have a batch of IPA to drink, I like to adjust my bitters by adding the torrified wheat, reducing the late hop additions, reducing the sulfate to about 150 ppm, and increasing the chloride to about 30 ppm. Stops me overdosing on hops.
Hope this helps,
There are only 10 types of people in this world. Those that understand binary, and those that don't.