@Chilli Jam Vans supply the only T6.1 specific springs on the market, so if this is your budget, Brett is your man. We can fit if you are near to us.
But also dependant on which way you want to go, we can also offer tried and tested coilover kits from KW, ST, Eibach, SoLow and Bilstein, so can offer lots of advice and information for your needs. We are also a dealer for twin-projekt, from Chilli. Coilovers , although more expensive than springs, offer height adjustment, and varying levels of comfort and handling dependant on which kit you go for. We offer the complete demo and fitting service, from our site in Bognor Regis. Every kit we fit comes with a full 4 wheel alignment, which I know not all carry out . We've lowered quite a few 6.1s now, so happy to talk through your options. All of our kits come as a mail order option as well, for your local fitter to do the job.
As and when it becomes available, and Im told they won't be long, I would recommend an ARB upgrade, works really well on a top heavy camper.
I always say with suspension, please try and drive the suspension you are buying beforehand. What someone tells you is best, is only their opinion, and their definition of comfortable or sporty will be different to yours.
Good luck in your search, and enjoy your camper - This forum can and will cost you money ;-)