Double check the Financial Requirement FM1.7 here:-
https://www.gov.uk/government/upload...ugust_2015.pdf
Section 5 - salaried and non-salaried
Also here:-
https://www.gov.uk/government/upload...ndix_FM_SE.pdf
Under the section 'Calculating Gross Annual Income under Appendix FM' for 13a and 13b
Strictly speaking under 13a your annual salary (equal to or above the stipulated income threshold ) is paid in 12 equal monthly payments.
Phil, based on what you've stated before your basic annual salary meets the requirement for Cat A Salaried.