Whats the difference between Plexiglas® and Perspex®?

Both Plexiglas® (most commonly spelt Plexiglass) and Perspex® are brand names of Acrylic sheet. Röhm GmbH, based in Germany, are the manufacturers of Plexiglas® whereas Perspex® is manufactured in the UK by Perspex International Limited. Both manufacturers supply a wide range of colours and thicknesses. Whilst the brand names Plexiglas® and Perspex® are different, ultimately the acrylic sheet that they manufacture is the same albeit each manufacturer might tweek the formulation to increase or enhance UV-resistance, light transmission or colour.