Fair play to him for having the courage to even walk through a recruiting office doorway but..... it’s just wrong, totally wrong.
HM Forces is all about uniformity, that’s why soldiers in infantry units in particular have always worn their own badges and adornments to distinguish themselves from other units(hackles, maroon berets, back badges etc). Indeed, my former regiment of the line wore the flash, which made us stand out collectively amongst other units.
http://www.rwfmuseum.org.uk/en_faq.html
If you want to wear the turban, you join a regiment where they do so. If none exists, you join another regiment and fall in line with the dress code.