Apologies for the delay, attached are photo’s of the heater vents. The one in the middle of the seats below the centre carpet is the outlet for the auxiliary (water) heater. The one beneath the passenger seat is the auxiliary hot air heater.
To date I have found both useful. The auxillary (water) heater - which doesn’t heat water, can be set remotely and is really useful to warm up the van before setting off on a journey.
The hot air heater is good as the temp can be set and will keep the van warm (albeit it can get too warm). It s also useful to dry out the van if its been wet or there is condensation before closing the roof.
As to whether you need both, I suspect not. The hot air heater is probably only really necessary for all year use.
I have both heaters - fortunately and unusually both were specified by the dealer on my pre-reg MP. I consider the warm air heater essential, even though we don’t generally camp between late October and early April.
In three ‘vans over 12 years we’ve always had either Webasto or Eberspacher blown air diesel heaters. It’s surprising how often we put the heater to use. For example: the Highlands in June, Dartmoor in April, the Lakes in October and even Provence on a particularly bad day in early June.
I wouldn’t specify a new van without the heater, despite the cost. Buyers like me who’ve owned a California, where the Webasto heater is standard, will expect there to be an auxiliary heater and the lack of one may subsequently have a deleterious effect on resale value.