The most common way to finance a van: fixed monthly payments over a set term, and you own the van outright once the final payment clears.
With HP, you pay a deposit (often 10%) then fixed monthly instalments covering the remaining balance plus interest over the agreed term. You don't own the van until the final payment is made — the finance company retains legal title until then, which is why the vehicle can't usually be sold without permission during the agreement.
A larger deposit, a longer term, or a stronger credit profile will all reduce your monthly figure — though a longer term usually means more interest paid overall. Try the PCP/balloon calculator if you want the lowest possible monthly cost and don't mind a final payment.