Hi David,
The actual process of changing the tax status on a van from commercial to private use is relatively straightforward, you simply ring up your local motor tax office (you’ll find your nearest one here) and tell them what you want to do. They’ll then shift you onto the old engine capacity-based tax system (you’ll pay €710 a year for a 2.0-litre engine) and the job’s done.
Except it isn’t, quite. You will need proof of insurance first, and insurers are, for some reason, reluctant to switch policies over. It’s worth finding a good local broker to help you get the insurance sorted out first of all.