Seems well overpriced to me, the vans probably only worth £800 without system.
The van will most probably be needing a new gearbox soon and definitely a head gasket if it's never been changed at 150,000.
They are decent vans but I reckon the van would of seen better days by now and will be ready for a lot of spending if a lot of the wear and tear parts have not already been changed or reconditioned.