Dave, it's been going on for a long time. One of the reasons I moved from medals to badges - not knowing that faking was just as much as a problem with badges !
As I stated earlier in this post, it is relatively easy to make up a set of WW2 medals including paperwork.It's a bit harder with WW1 groups as the paperwork is usually more detailed.You can get fake death plaques, fake named boxes, faked and aged paperwork and medals can be re-named.A real nightmare for collectors as, for an example, a re-named military medal,military cross or DCM group can be upwards of £1,000.Throw into that mix an original medal that is a replacement for a lost medal and the 'R' for replacement has been carefully removed....
Mark