English Base & Crystal Malt

I'm brewing the ESB from BCS and the recipe uses:

12.00 lb UK Pale Malt (2 Row)
0.5 lb Crystal 15L
0.25 lb Crystal 120L

If I was to use all English malt available at my LHBS, does the following grain bill look like equivalent to the recipe? Is it worth switching from the Briess products for the crystals?

12lb [Crisp] Maris Otter
0.5 lb [Crisp] Cara Malt (18L)
0.25 lb [Simpsons] Extra Dark Crystal (150L)

Yep. Your modified recipe will be slightly darker, but probably not noticable. The flavor change would be minimal and probably not perceptible. But the great thing about this hobby is the experimentation. So for the minor cost difference, I say try it your way.

I don't brew any British recipe without MO in it. Flavor here will be a bit maltier, which I actually like in an ESB.

British crystals are quite different and much better suited for English ales. Your recipe is better.

You will always be better off using traditional UK malts when brewing British styles.

Also, there is indeed a difference in flavor between the US and UK crystal malts and it is very apparent when you drink enough of the real stuff. The Simpsons extra dark crystal is a great grain and you wont get the same flavor from an American 120L. The closest thing to it would be a Belgian Special B. Also, remember that many US specialty grains are made from 6-row, whereas you won't find anything but 2-row crystals in the UK.

Edit: the same is true for US/UK hops. A US fuggle and goldings are vastly different than one from the UK.

I'm sure the way the recipe is written (in the original post) intends for an English base malt (Maris Otter, Golden Promise, Halcyon).

Sourcing specific grain has been one of the coolest aspects of all-grain. 95% of this recipe is base grain, so I'm sure the difference between US 2-Row and actual UK 2-Row Pale Ale Malt would be noticable.

I only have experience with the Marris Otter. It's interesting to hear that British crystal can make such a difference. I just got done brewing a brown porter, maybe I'll brew up a 2.5 gal batch with all British crystal to see the difference.

I think JZ first brewed it with Great Western crystals. They are not as sweet as Briess. English crystals are different form maltster to maltster too.