Tosh you don't need a transfer pump. Do what I have done - the bottom of my tank is only 2ft 6" off the ground - put a 3" transfer hose direct to the outlet of your IBC, reverse up, drop hose into van tank and you will get 400L assuming it is a flat tank in less than 5 minutes. (I do and my IBC is only 600L so pressure from a 1000L will be greater especially if it is topped up - the key is in the hose diameter.)
To fill a back pack - take 2 x 25L drums with you and top up as you need it (you can also use this reserve to top up your van tank if it runs out on your last house.)
Also where the pipe from your van tank comes out to go to the pump (bottom left corner as you face the back of the van usually) put a t- piece with a tap and a length of hose so you can put the backpack or bucket - on the floor and top up direct from your tank by gravity. (A bit slow through a half inch pipe but it works.)