Needleworth campers is a reseller for camper king campers whereas Cambridge I think build their own.
I think both produce good looking campers with nice wheels etc but try to look past that to the quality of the conversion itself and the spec of the van it’s based on. You can always add the wheels etc later.
We have just had a conversion done and I wouldn’t say we made it perfect choice with the converter but it has what we want.
We ended up spending more on the base van than I budgeted for but still only a t28 102 5 speed and going from a 7 speed auto 5 series BMW I love it and can’t stop smiling driving round it’s great. Like you it is something I’ve been dreaming of for a long time and I never thought we would do it.
Enjoy the process, whether ready made off the peg or base van conversion. No decision will be perfect, no choice will be without naysayers just do to get it done and get camping! Happy Hunting!