I think you could download the orchid occurrence data from GBIF(http://www.gbif.org) and some virtual herbarium. Then you could visualize the distribution with ArcGIS software (e.g. Divagis). Of course, the potential distribution range can be deduced by species distribution modeling (e.g. Maxent).
Hi Spyros, In France, an atlas of orchids has been published in 2010 for the metropolitan territory. It presents the distribution of each species in a grid of 10 x 10 kms. I think there similar orchid atlas at least in Germany, UK and Switzerland. Did you find similar orchid atlas in other European countries? Cheers, Bertrand