I believe the Heligoland stamps also come forged or faked. Do a search on SC, I remember a topic about that, don't collect them myself. Some can be expensive stamps but the forgeries are not.
Try
www.delcampe.net also for searching, an auction worldwide site based in Belgium.
The India stamp looks common or minimal value. the Swedish I am not sure. The Hong Kong stamp I think comes in different versions (watermarks different?, different issue dates for different printings?), the guy on that stamp is King George 5 of KGV when searching.
Sorry for telling you how to search. I like searching and find not everyone knows all the tricks to it (I don't either, always learning).