1st Recipe, a Clone, would like opinions

We all seem to have that beer. You know. The best one you ever had, but only had once, or just kinda remember the recipe? Well, that beer for me is Summit Brewing's ESB. Since they no longer make it, I contacted them, and they were nice enough to provide me with a copy of the sell sheet for it.

HERE

So, I've been playing with BeerSmith for a couple of months, and this is the recipe I've come up with. It hits all the numbers almost dead on (except color, which i'm not too worried about). I would appreciate any reviews / comments / changes that would make it better:

3 lbs UK 2-row
3 lbs Simpson Golden Promise
3 lbs Crisp Maris Otter
1 lb Crystal 60

1.25 oz Target @ 60 min
1 oz Fuggles @ 1 min
0.5 oz Northdown Dry Hopped

Wyeast #1968 - London ESB

I'd play with the Target & Fuggles quantities to get ~47 IBU from the Targets, and the remainder from the Fuggles (based on their AA, just using Beersmith's default values for now).

Primarily what I have questions / would like help with is:

1. This recipe distinctly calls for 3 different, 'base grains.' I've never used Maris Otter or Golden Promise before, but i'm looking for that nice malty, slightly sweet flavor this beer had. Should I use some other ratio than the 1:1:1 I have?

2. When it comes to dry hopping, how much and for how long? I've read all different things, but this beer had a nice slightly grassy flavor, but it wasn't like chewing on weeds.

3. Lastly, what alternatives are there to Northdown, for dry hopping? I can't seem to find a seller online, and my LHBS doesn't have any (and is 2 hrs away).

Totally forgot I could do this:

Recipe: Summit ESB Sell Sheet
Brewer:
Asst Brewer:
Style: Extra Special/Strong Bitter (English Pale Ale)
TYPE: All Grain
Taste: (30.0)

Recipe Specifications
--------------------------
Boil Size: 6.52 gal
Post Boil Volume: 5.98 gal
Batch Size (fermenter): 5.00 gal
Bottling Volume: 4.60 gal
Estimated OG: 1.053 SG
Estimated Color: 9.2 SRM
Estimated IBU: 47.2 IBUs
Brewhouse Efficiency: 72.00 %
Est Mash Efficiency: 82.8 %
Boil Time: 60 Minutes

Ingredients:
------------
Amt Name Type # %/IBU
3 lbs Golden Promise (Simpsons) (2.0 SRM) Grain 1 30.0 %
3 lbs Pale Malt (2 Row) US (2.0 SRM) Grain 2 30.0 %
3 lbs Pale Malt, Maris Otter (3.0 SRM) Grain 3 30.0 %
1 lbs Caramel/Crystal Malt - 60L (60.0 SRM) Grain 4 10.0 %
1.25 oz Target [11.00 %] - Boil 60.0 min Hop 5 46.5 IBUs
1.00 Items Whirlfloc Tablet (Boil 10.0 mins) Fining 6 -
1.00 oz Fuggles [4.50 %] - Boil 1.0 min Hop 7 0.7 IBUs
1.0 pkg London ESB Ale (Wyeast Labs #1968) [124. Yeast 8 -
0.50 oz Northdown [8.50 %] - Dry Hop 5.0 Days Hop 9 0.0 IBUs

Looks like my kind of beer. Let us know how it goes.

Looks great.
1) I would do away witht he 2row and up the GP and MO to make up the difference.The reason being,the British base malts will give you the malty backbone, but the plane old 2row will take away from it a little.
2)dry-hopping with half an ounce will just be there,but not in your face. I do a 14 day primary(no secondary) and add my hops at day 5. As for the substitute....try Challenger if you can get hold of it.
Cheers

Switched to 5lbs GP, 4lbs MO. Was able to get a hold of some northdown.

Other than some efficiency problems (new burner, much higher boiloff), brewday went without a hitch. Smells great, can't wait until it's bottled, carbed, and waiting to be enjoyed. Thanks everyone for the help so far.