About a year ago, I was on a coach traveling from Haworth to Fountains Abbey in Yorkshire. Along the way, I saw what appeared to be a bubble city! It looked like the aliens had landed right there in Yorkshire! Does anyone know anything about this? I've been wondering since I first saw it!

I don't know that specific road - but I'd guess what you saw were military communications bases. There are bubble-like antenna housings all over northern England. Like near flyingdales in the Yorkshire moors.

Were they large, light colored spheres - sort of geodesic dome shaped? That is what other ones I've seen look like.

What you might have seen was the Eden Project. www.edenproject.com/ It's in Cornwall though.

What you saw was Menwith Hill US National Security Agency (NSA) electronic monitoring station, one if a series of bases around the world that send information to NAT HQ at Fort Meade, Maryland.
Located just off A59 near Harrogate, it has been controversial since its inception in 1996 for its possible part in the 'Son of Star Wars' global defence strategy.
You can read more about it in Yorkshire CND site:
http://cndyorks.gn.apc.org/mhs/index.htm
Those giant golf balls are called radomes hiding satellite dishes for monitoring purposes. The base employs about 1,800 people, most of them from US.
Janis' reference to Fylingdales is about another station, this time an anti-missile early warning radar hidden inside a giant concrete pyramid-like structure. There is a link to it in the above site.

I checked the link, and it was the Menwith Hill NSA monitoring station. Thanks so much for your help! The mystery is solved.