The ARB is the statutory independent public interest body established by Parliament under the Architects Act
1997 to regulate the UK architects’ profession in the public interest.Anyone wishing to use the services of an
architect should check the Register of Architects at www.architects-register.org.uk.Only registered architects are legally allowed to use the title ‘architect’ in business or practice; if they are not on the register they aren't
The ARB web site has a very useful section for the public:
There is a lot of information on this site generally about appointing an architect, working with an architect, expressing
concerns and making formal complaints. This is where you should go if you need information in this regard.