I have the same problem! I'm trying to get down from about 30 to about 10!
I don't make lagers but I guess Saaz, Hallertau, Tettnang are the standard hops. However, a smart move may be to use the NZ hops that were bred from German noble hops, like Motueka, Wakatu and Pacifica, as these are good in American style pale ales and I believe they make good lagers too. I like Motueka a lot.
For English bitters I like First Gold, Challenger, EKG, but all are reasonably similar. Challenger could be a good option as it is excellent for bittering as well as aroma. (Mind you, I've just had a glass of Marble Wood Street Bitter at the Marble Beerhouse in Chorlton and at just 3.6% ABV it was really excellent - and is 100% Admiral apparently, so that would be a good alternative).
You could also consider Progress - bred to replace Fuggles, I actually prefer it, and it has a mid-range AA%. It blends really well with Challenger and EKG. And First Gold, no doubt.
As far as American hops go, and I would struggle to pick just one - I think Centennial is a really good hop that is really versatile across different styles of ale. Cascade likewise. Simcoe is another good option. It is more piney than Centennial, which is fruity. They both make great single hop ales, and blend well with other hops too. Cluster is another good option, according to Seymour, and my limited use of it backs that up. And I like Columbus, it does everything - if you like fruity and dank.
So my suggestions would come from:
Challenger or Admiral - both good bittering and aroma
Progress - good dual purpose and complement other English hops well
First Gold or EKG - two great english aroma hops
Motueka - really versatile for ales and lagers
Saaz - classic lager hop
Centennial or Cascade - both very versatile and classic American flavour
Simcoe - really versatile, great flavour, excellent bittering hop
Cluster or Columbus - two distinctive multi-purpose hops
I've got you down to 8, I think.
