There are a variety of reports on the internet about this compound check out bluelight and erowid also see TIHKAL. Overall reports seem to be rather negative some negative side effects have been reported. There have also been overdoses reported. However it has been sold as "LSD" on blotter and sugar cubes and thus people were taking multiple doses. I have no personal experience with this compound however I bet that like many things if taken at the right dose it probably could be enjoyable. Positive reports do exist. SWIM would just start with a very low dose 2mg and work her way up.
Many types of isomers exist therefore the term "true isomer" is a bit ambigious. 5-MeO-AMT is a structural isomer of psilocin but not a positional isomer. In the US law positional isomers are specifically mentioned for mescaline and psilocin (for example) however the term structural isomer is not used. A positional isomer and structural isomer differ in that in a positional isomer only a few functional groups are switched around whereas a structural isomers may lack completely the parent skeleton and have completely different functional groups yet the two compounds still have the same molecular forumla. Many things can be structural isomers (only requirement is having the same molecular formula) thus it would be ridiculous and difficult to make structural isomers illegal. US law says positional isomers, not sure about UK but I bet it is similaur.
In SWIMs opinion 5-MeO-AMT is not a positional isomer of psilocin as the skeleton differs and the functional group changed (from an OH to a MeO) however SWIM is sure that if they wanted the government could find a chemist who would say otherwise (although they would be wrong
). Thus it would come down to who has the better experts (most $ to spend). Unless SWIM is planning to import large quantities it is unlikely that the gov would target someone in possession of a personal amount of an ambiguous compound (although you never know).