Bailey's Internal Water Tank

We bought a Bailey a year ago and at first were delighted with a supplementary internal water tank.  Up until then we used a watering can as an “emergency reserve” for the Aquaroll.  The watering can was also used for filling the toilet flush tank.  The problem with the Bailey tank is that you cannot fill it in situ (although it might be possible to modify the system to do this).  So, take seat off of locker to gain access, reach down and undo cap to remove pipe, go to the outside of the van, remove the tank, fill it, wheel it back then lift heavy tank back into the compartment, back inside the van and fiddle around refitting cap etc. etc.  …. if you have a Bailey you know what I mean!

So, when the Aquaroll runs out you can change over (manually inside).  Remove the seat, lift the locker …. you get the idea.  Then, before moving off you have to remove the tank to drain it properly or you end up with 120 kg nose weight (no, I am not exaggerating).

Do I go back to the watering can or am I doing something wrong?