Whilst the term Interior Architect is commonly used in some countries, under the 1997 Architects Act it is illegal in the UK to refer to yourself as an Interior Architect unless you have had the education, training and experience needed to become an architect and are registered with the Architects Registration Board which is the UK's statutory regulator of architects.
There is no statutory regulator of interior designers in the UK and currently anyone, regardless of education, training and experience is able to call themselves an interior designer. In the absence of a statutory regulator, the BIID is the only UK professional body for interior designers that has been awarded Institute status. The term Institute is government regulated and only awarded to professional bodies of the highest standing. The responsibility of a professional Institute is to set the highest standards of practice for its particular profession. Candidates evidence that that have met these standards by successfully completing the BIID Professional Pathway, after which they become a Member of the BIID.