I found the G line not especially lively to ride, possibly because I'm used to a lithe and fast rolling 20 incher. It wasn't unpleasant, it just didn't feel anywhere near as flighty a bike that cost barely a fifth the price.
And if you're going down the 20 inch route a Tern style fold is perfectly adequate on the choo choos, and I've experienced first hand.
I'm still not totally sold on the G-Line.
When I first test rode them, i was probably one of the first to do so - this is not a brag, but is important later on*.
The small was too small, so I only took the large out for a ride, but I agree that it didn't feel particularly nimble.
I went back to the Brompton Junction last week and they do now have a medium test bike. I didn't take it out as it was ten minutes before closing and I didn't have my cards with me for a deposit anyway. So I just sat on one for size.
*It felt like it had done 100,000 miles. Felt very sloppy - like everything had worked loose. I am going to go back and try it out for real, but didn't inspire much confidence if I'm honest. Compared to when I rode one when it was brand new.