I had a carrera transit in my shop at the same time as having two different Brompton's in and apart from being a slightly more bulky design and a bit heavier (really not by much) I thought it was a great bike for the money. Very comfy and smooth ride and most importantly, very easy to fold down. I would never normally recommend a carrera so this is surprising me as much as it is probably surprising you
Don't get me wrong though, you can tell the extra quality in the Brompton's, but I was reaaaaaally struggling to see the £1000+ price difference