You can self fund a course with global at Gloucester, however ATC training courses, by their very nature, are a full time commitment. The courses run Mon to Fri for between 7-10 weeks depending on what course you are on.
I don't think there is any way that you can do a little bit here and a little bit there whilst holding down a full time job. The courses require you to spend time on ATC simulators along with classroom based lectures. No training college could possibly accommodate someone who starts the course on day one, but has to leave mid way through the next week.
Sorry that's not the answer you were looking for.