Oh, I don't doubt that it's a fantastic course.
The clue is in the OP's use of the word "retired". A student loan is largely irrelevant when you're no longer earning, and that's a helluva lot of money to spend on improving your bass-playing with little prospect of earning it back.
What would a good bass teacher charge for tailored one-on-one sessions? £30 an hour? £50 an hour tops? Even at that rate, that course would buy 127 personal sessions in your own house, twice week for 15 months.
Think about it.