Any idea on.....

[Cereal]

How this looks:-

Amount Item Type % or IBU
3.00 kg Pale Malt, Maris Otter (5.9 EBC) Grain 66.7 %
1.00 kg Lager Malt (3.9 EBC) Grain 22.2 %
0.50 kg Cara-Pils/Dextrine (3.9 EBC) Grain 11.1 %
20.00 gm Northern Brewer [8.50%] (60 min) Hops 27.8 IBU
20.00 gm Cascade [5.50%] (15 min) Hops 8.9 IBU
50.00 gm Hallertauer [4.80%] (1 min) Hops 1.7 IBU
30.00 gm Cascade [5.50%] (Dry Hop 7 days) Hops -
0.20 tsp Irish Moss (Boil 10.0 min) Misc
1 Pkgs SafAle English Ale (DCL Yeast #S-04) Yeast-Ale

Beer Profile

Est Original Gravity: 1.056 SG
Est Final Gravity: 1.015
Estimated Alcohol by Vol: 5.4 %
Bitterness: 38.4 IBU Calories: 468 cal/l
Est Color: 10.8 EBC

Any comments gratefully received, it's based on some grain and hops I have left over from my previous (1st) attempt and just a few random picks!

Only going for a 15 Lit finished batch due to poor efficiency on my 1st go, I'd rather try to improve my skills with a minimum of waste.

[Barley Water]

Well, for whatever it's worth, I think that the Cascades will completely cover up the Hallertauer. If I were doing it, I would probably just substitute the Hallertauer for some other "C type" hop, you are going to get the pine tree/resin/grapefruit anyhow, you might as well get a lot of it (Simcoe might also be fun). Since the beer sould be fairly dry as you are adding no crystal, you might as well make a hop bomb, as always, your milage may vary. Have fun.

[Deebee]

seems like a lot of carapils to me.
In that size grist i would likely drop it to half.