Just a point ,Whale and Truma inlets are different to each other , the kit you have shown has the whale fitting and an adapter to fit a Truma inlet, if you have the truma inlet ( pistol type fitting) then you could by the truma only version a lot cheaper than the one you have shown.
I have never used on , preferring the internal float ball valve in the aquaroll. Whichever one you opt for remember to disconnect it when away from the van , I had a customer who didn't and a fitting inside the van let go and the van was flooded to a depth of 25-50mm, fortunately nearby caravanners spotted the water pouring out of the drop holes/door and turned off the supply