G'day!
Plenty of furriners on the Dutch Barge Assn. forum at barges.org (I think you have to be a member but it's very useful and not just for big boats)
We keep a shared boat on the mainland (currently in Gent). We usually find a marina which is cheap for the winter months and much more secure than an unattended online mooring. We winterise her ourselves (an easy job if the boat is designed properly), keep the batteries topped up with a solar panel. Canal levels don't usually fluctuate much, but there's always someone around to slacken lines if necessary. If on a river you must make sure that you have a floating pontoon or adequately long mooring poles. For our share boat, we book our winter mooring about six months in advance. It may not be necessary to go so far out in the UK unless you are looking in a popular area.
Martin/