Hi,
I'm the Technical Manager for a company making 'stickers'. I know that the trade use the hairdrier trick to remove the film but this tends to leave the glue behind. If you do use this method, using surgical or methylated spirit should get the glue off but be careful of the van finish as this may be affected. The WD40 trick is also useful and less likely to cause harm to the finish. I would be happy to answer any other questions related to this issue.