Do your PPL first, if you have not already done this and hour build, when starting ATPL, it will take more time than what you do at London Met, around 4 -5 hours, 6 days a week, in addition to London Met.
One great tip, save ONE exam (Comm), until you have finished your hour building, this way you have 3 years from this final exam to complete your CPL/IR - so you get maximum time, in case money is an issue.