I have a 2011 plate renault traffic, had it from new and have always loved the van, on a run I still get 35 plus to the gallon, I have a 650l tank and only do window cleaning now. Smaller vans may be great on economy but space really is a premium, transit/traffic size is ideal, they drive like a car and parking and so on is pretty much straightforward, go larger and that most definitely becomes an issue as does fuel economy.
Alas although my van is low milage for it's age, she is also an old girl now and every year she fails the MOT on something, usually ball joints or track rod ends (very common on traffic/primastar and vivaro) I'd love to get a new (er) transit custom but I'm also at the tail end of my working life! 😪 at some point I'll have to replace the old girl ... it's a hassle on the horizon I could do without!