I'm not having a lot of luck finding the english pale either locally or on the web. I would just go with the Light LME. You are correct in saying that you will get most of the flavor and color from the grains steeped.
As far as your total volume boiled goes. Since you are steeping your grains first( I assume) They should be able to get the most out of those. Your LME will have their own amount of fermentables all ready to go. Whether you boil 2-7 gallons that should be the same. The major difference is going to be your hops utilization. The more volume boiled the better/more IBUs your going to get in less time. I like to plug all my recipes into Beer Calculus . homebrew recipe calculator
and adjust things if needed. I hope this helps