You could try putting it on a classified advert on Ebay, there's also Gumtree. I wouldn't put the price down just yet, you often find that it takes a while for the right buyer to come along so try and be patient. They were like buses when I sold my old van last year.
It's a good time of year to sell but it's worth reviewing your advert to see if it's as effective as possible. Make sure there are lots of good photos, including a few holiday snaps on campsites as you're selling a lifestyle, not just a van. Put as much detail into the description as possible. The photos get the first interest but it's the little details that will have people going back and mulling over the advert whilst considering giving you a call.
It's worth preparing a list of the points that you want to highlight to any prospective purchasers when they visit. It's easy to forget something in the short window you get to make a sale. Be realistic with any offers you get if you haven't had much interest. If you've got a load of buyers lined up to visit then say so to the prospective purchaser and stick to your guns on price. Above all, make sure the van is spotlessly clean.
Best of luck!