With a van, the 4m needs about 7m (across the front) by 6m, and the 5m about 8m by 7m. The Classic figures assume you're using reducer poles; without them, add about a metre each way.
Pitch sizes vary a lot between campsites, and many are around 10m wide. The widths below are measured across the front, looking at your van.
With your van
Classic 4m: 7m x 6m with reducer poles, or 8m x 7m without.
Classic 5m: 8m x 7m with reducer poles, or 9m x 8m without.
GlawningAIR 4m: 7m x 6m.
GlawningAIR 5m: 8m x 7m.
Tent only
Classic 4m: 5m x 5m with reducer poles, or 6m x 6m without.
Classic 5m: 6m x 6m with reducer poles, or 7m x 7m without.
GlawningAIR 4m: 5m x 5m.
GlawningAIR 5m: 6m x 6m.
Why reducer poles help
With reducer poles you can peg the tent out about 30cm from the edge of the groundsheet. Without them, guy ropes usually need at least a metre.
