Looking at the BB kit recipe online:
6.6 lbs light LME
1.0 lbs amber DME
1.0 lbs Crystal 40
0.5 lbs Victory
OG = 1.061 - 1.065
Hops
1.0 oz "bittering" (60 minutes)
3.5 oz "aroma" (5 minutes)
IBU = 47 (based on 2.5 gallon partial boil)
The sheet I found doesn't list the hop varieties.
If I were trying to make a 5g batch of this recipe, I'd make my first attempt using:
12 lbs of UK 2-row (7.6/0.75 / 80% efficiency)
1.0 lbs Crystal 40
0.5 lbs Victory
For future batches I might experiement with Maris-Otter depending on how I liked the result. I'd probably make the second batch using 100% maris-otter, and then decide which I liked better. I might even end up blending the two to decide what proportion of each I liked the best. Then I'd modify the recipe, based on the results of the blended tasting.
For Hops, you'll have to decide what variety to use (unless the actual kit tells you what to use). Assuming not, as an english style I'd stick with english hops: Kent Goldings, and/or fuggles. I'd probably stick with Goldings until I'd worked out the grain bill above. Then I might experiment with splitting the hops between the two varieities.
NOTE: your amounts of hops will be different because you will be doing a FULL boil versus the partial boil. Beersmith will work that out for you, though. Just know that it will be different and design to the IBU target, not the weight.
Unless......you did a full boil with the amounts that they gave you. If you did a full boil, and used the full amount of hops in the kit, then you will have to work out what IBUs were in your previous beer. That's easy enough. Create a replica of the extract recipe including the hop weights, and using a partial boil (2.5 gallons). Adjust the bittering hop amount until you get 47 IBUs. Then change the recipe to a full-boil and see what happens to the IBUs. I don't remember the exact relationship, but I'm guessing you will end up somewhere around 65-70 IBUs. That's about where I would start, if I were designing an IPA with this grain bill from scratch, anyway. So, that's a good starting point if you don't want to go to the trouble above.
For yeast, again the recipe doesn't say.....I would use WLP001.
I guess part of the point of the above, is that replicating a recipe is a multi-batch process. There are some split-batch things you can do to minimize the time required. You could mash ten gallons of wort and split that into two separate boil kettles. Then you could use different hops in each of the two batches. But, in the end....you have to brew a batch, taste it, and decide how you want to adjust based on what you are trying to do. You may even end up diverging from the original goal of REPLICATING the kit....you may decide you like one of the experiements BETTER than the kit.