I would not be happy with a 400l tank in a combo, 400l +400kg plus say 25 kg for the tank, add the frame another 25kg (or strapes 1kg diy option added for matt)
15kg for hose reel with 100mtrs of hose
pump ect about 5kg, fuel 35kg, trip signs 5kg, you 50kg, ladders if you have them 10kg... these are only the things that came to mind straight away and weights are guestimet. 250 would be safe and 25l barrels if you needed them