Hi Ash, tell them you want to strip the extra's down ie; you don't want all the useless rubbish like windscreen cover or 'free' breakdown recovery (you can source this yourself much cheaper). At the end of a quote the insurance people will read you a great long list of what your insurance covers, tell them you don't want any of it and that you just want to legally get on the road....... Offer to pay a higher excess premium in the event of a crash, sometimes the higher your excess the cheaper your premium and if your van aint worth a load then if you was to have a crash you would probably scrap it anyway (although if you have a new van or it's worth a few quid then keep the excess low)
Shop around for a small independent broker, they are much more likely to help you out. Also ask if you could get a discount if you got your tools insured via them at the same time as well as personal insurance against injury, sometimes paying out for them things can actually bring your premium down. Try anything, haggle haggle haggle mate