Described as the new depron, EPP foam is strong, flexible, light and
now available as sheet and block in 3 colours.

You can make virtually any type of model from a super tough fast
combat wing to 3D foamy models and ultra light indoor models.
Due the nature of the material, the sheets can vary in thickness by +-
0.5mm, the sheets can have a few black spots aswell.

They are available here;

http://www.flyingwings.co.uk/store/product_info.php?products_id=764 
White EPP Sheet 9mm x 600mm x 900mm
[FW0226] £7.95

At £7.95 +shipping per sheet 9mm thick it is very expensive in UK so if you guys have a contact in Germany, that is the place to buy this from.

Originally developed for motor vehicle and aerospace applications, EPP is impact resistant bead cell foam. With good memory effect due to the molecular structure, this material is excellent for crash / impact protection, used extensively in crash helmets, car bumpers, and aircraft cockpit.
EPP models are typically covered with cross weave and Coloured Tape, or a low temperature heat shrink covering.
EPP is not suitable for surfaces that you intended to sheet with balsa wood.

Rigid EPS foams are better suited for covering with sheet balsa.

WORKING WITH EPP FOAM 
 To ensure a good adhesion to EPP always spray any foam surface with 3M-77 type Spray  Adhesive before applying coloured or cross weave tape. Or latex adhesive, this helps the tape to stick.  You can even spray a light coat on the balsa elevons before applying coloured Tape.  After you apply any self adhesive tape to your model, take a credit card shaped piece of cardboard and smooth the edge from the middle to the edge. Use it stick like a squeegee to iron out any remaining air bubbles and smooth the tape to the foam, then use a covering iron on the lowest temperature to iron down the sticky tape to the foam. Warning go gentle or you will warp the EPP. It only takes a few minutes to do this to a completed glider, and it really makes the whole covering job look great. It will also increase the efficiency of your model by making the smooth surface fly that much better.

GLUE'S COMPATIBLE WITH EPP FOAM   (ALWAYS TEST ON SCRAP BEFORE COMMITTING TO YOUR PROJECT) ; Foamsafe cyano (superglue) - latex based glue - uhu por-2 - part epoxy - hotglue gun. You can decorate with foam friendly felt tip pens and paints

Is epp sheet similar to pp sheet? I found pp sheet locally but it is too flexible to build a plane.

@flyer
too flexible mean it isnt suitable