To have a career as an architect and work for a Residential Architects Mayfair way such as https://www.rbddesign.com/architectural-design/residential-architecture-london/architects-mayfair/ there are a number of qualifications that you will need to have.
In order to continue after your GCSEs into other qualifications that will see you work your way towards a career as an architect, you will need to have achieved at least 5 GCSEs at grades 9 to 4 (A* to C) or equivalent qualifications. Of these 5 GCSEs you should have achieved 9 to 4 in English, Maths and Science.
Once you have completed your GCSEs you can then go on to take A Levels or equivalent qualifications. This will then give the points that you need to apply for a university degree if that is the route that you want to take. When you look for a degree it is important that this is a degree that is recognised by the Architects Registration Board. During this course you will undertake a year’s worth of work related experience and a final exam.
Other routes can include undertaking an apprenticeship which will see you taking the same kinds of qualification as a degree but this will be interspersed with your attendance at your chosen workplace. This then means that you gain practical, industry experience alongside your academic training. You can qualify through this route in around 4 years.