I read it as even easier than that.....

1. a) A copy of a current membership card to a recognised Collector’s Organisation; or
b) Evidence that you are a bona-fide collector by attaching including a list and/or
photographs of the Prohibited Weapons you currently possess or propose to collect
to demonstrate;and
2. A dated and signed letter recording each prohibited weapon type you propose to
collect and detailing the theme of each type of weapon in your collection. Themes may
be of a commemorative, investment, historical or thematic nature, or of a particular
range or era. You should provide as much detail as possible (e.g. valuation
certificates, collector club endorsement etc) to demonstrate that your collection is/will
be of obvious and significant investment, commemorative, historical or thematic value.

So you say your a transformer collector, have all figures from 1984, and one of those is an imitation firearm. include a catalouge scan and you should be done.... likewise same for MP Megs