If you have equivalent academic qualifications then you will be asked to provide a Letter of Comparability from UK NARIC before attending your first selection day. The Scottish educational qualification equivalents are detailed in the FAQ page.
Where does it say that equivalent qualifications must be outside the UK?? It just says if you have equivalent qualifications then please provide a letter of compatibility. Does not mention that they have to be outside the UK so on this basis, I would assume that you are fine.