Forget about maximum HR. look at the sticky at the top of this forum, which gives a method for testing for your aerobic threshold. Then set your HR zones based on that threshold. I use the following: Z1 65% - 80% threshold. Z2 81% - 88%. Z3 89% - 93%. Z4 94% - 99%. Z5 100% and up.

Most of your training should be in Z2. The border between Z2 and Z3 is a good place to be to build aerobic fitness. If you want to increase FTP, do some Z4 and Z5 intervals a couple of times a week.

Have a look in the racers forum on this site. There's a sticky at the top of "The 33 - road bike racing" with a huge menu of suggestions for interval training. And if you take up Caloso's suggestion, and buy "The Time Crunched Cyclist" do yourself a favour and start with the beginners programs. The "experienced riders" programs are strenuous and will burn you out unless you have a biggish base.