Oxford’s M.Sc. Software Engineering will accept applicants with enough work experience in lieu of a Bachelor’s. Several of the University of London’s constituent colleges offer individual courses from Master’s degrees as individual professional awards or short courses (nomenclature varies) and successful performance will get you admitted to the Master’s proper. If you see a Master’s from U London and it doesn’t explicitly say it’s available to study independently as a short course you can still email them to inquire.