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I've just had a look at that BC training plan.
For a start, four weeks isn't much training to expect much return. Also, the plan involves a lot of vo2 and anaerobic work. While it's important to train all the physiological systems, gains in FTP are about muscular endurance and spending ever increasing times at threshold. So, lots of over/unders and increasing intervals at sweet spot/threshold.
Commuting for about 18 months 21mi round trip. Started doing regents laps and rollers about January and starting doing some of the British cycling plans in Feb. Before that was playing rugby to a fairly high level.