we're planning to head out into Europe in our camper van for about 10 days next summer - our first trip in the van. a hugely broad question, i am aware, but any ideas about where we should head, combining cities/countryside and not too warm, there and back in about 10 days including a night each way in Calais? it's been difficult to find help on planning itinerary - thank you for any inspiration!

Ten days will not get you to Spain from Calais, not unless you plan to only drive the entire time. Stick to the Benelux and the Rhine valley for the 8 days that you actually have traveling.

i'm sorry - i should have added the countries tagged are only prospective added because the forum prompted my to and should probably be disregarded.

If it was me - and I only had 8 days in a campervan . . . I'd stick to N/NW France

Stick to France and Belgium.... the later will have more of interests.
I assume this is your own campervan?

Do you have to get the ferry/tunnel to Calais? Have you thought about getting one from further west, to further west in France? Then you could explore Brittany easily.

Alternatively get the ferry to Dunkirk, which tends to be cheaper anyway, and explore Belgium, French Flanders, and/or the Netherlands.

If you are sticking with Calais then consider driving west to Normandy and exploring there. Plenty of things to see and do for 8 days in that area. Or as suggested above head for the Eiffel mountains and Mosel valley, in Germany.

Consider getting a Camping Card International, from the RAC or AA (or the Caravan club). It makes life easier at campsites in Europe, and may even get you a discount or two.
DOn't forget your green card and EHIC either.