Throwing in my Two Penn'orth here.
My fifth HPA style beer is currently fermenting, and it is my go to beer, call it my house brew at the moment. I have tweaked the recipe based on what I have in stock, and for the last few the hop additions have been Target for bittering and EKG for aroma.
Here is my experience:
The first clone used yeast cultivated from a bottle of Butty Bach - the yeast is fantastic as a top cropper, but I found it was fairly neutral. Don't get me wrong, seeing the souffle-like krausen on the beer was a thing of beauty, but after a few brews the faff of cropping and storing yeast made the process unenjoyable .
My clones too have been darker than HPA, so they must use extra pale MO.
Clone 2 was an exact copy of the first and tasted slightly different, but still excellent.
Clone 3 I swapped the Target for Magnum. I used a new cultivation from Butty Bach and it attenuated higher so went down to 1.006. It still made a good beer but was a bit drier, was 4.4%. It was probably a bit more like Holden's Golden Glow or Bathams which was a result in my book as these three are probably my favourite beers.
Beer 4 (I've stopped calling it a clone) I replaced the 430g of wheat with 250g of torrified wheat based on what I had in stock and by this time I had ditched using liquid yeasts and used MJ M36 liberty bell instead. This beer was awesome. I find the M36 imparts a slightly sour flavour to my beers making them very comparable with Bathams or Golden Glow and just to my taste. I also dispense from a king keg and find that this beer conditions very quickly and is drinkable within a week. It spent 14 days in the FV at 19degC.
The fifth variant (in FV now) has dropped the wheat and is just 4.4kg of Maris Otter with Target and EKG using M36 yeast. It's been in a week and is first tasting following a gravity reading after 7 days was very similar to no. 4.
I have experimented with water treatment as well, my water is very hard (230-240) and previously I have treated the mash with 12ml CRS and 2.4g gypsum then 27ml CRS for the sparge with 5.2g gypsum and 3.3g epsom going into the boil.
For no.4 I left the water treatment out and I don't think it compromised the beer.
Anyway in summary - I've brewed 4 very quaffable beers based on HPA and will continue doing so. The thing about homebrew is if you want a carbon copy of HPA - forget it without serious money and time investment, but a carbon copy is not required, just a beer that is the same style and is to your taste.
Happy Brewing!