Avoid Vanguard markers.
As Dusty said, if you get a working one then great. Poor quality control. Too many problems. No UK support anymore (only people who do still fix them is Foot and a couple of old techs, but they no longer get spares from Frank in USA).
If you get a pre 2013 Demon, then stock up on Diaphragms! Vanguard have no more in stock. They cannot get more. If you have a diaphragm issue and no spares, it is a junk gun or a £150 upgrade to 2013 internals... oh and then they have stopped polishing internals, so you have rough edges that shred orings.
Frank Connell is the worst thing that has happened to Vanguard.