I use wickes transfer pump, from there website its about £40.
If your going to empty one ibc in more than one van on the same day I would not use standard hose and hoselocks to connect the 2 as it is slow to level the water.
I use inch hose and connections that I made up myself, the ibc connections are quite expensive to connect the 2, I found some for about £17 each yet they want £12.95 postage (real costs of postage £4 max) hence why I made the fittings myself, I got what I needed from a local industrial pump supplier.