So, train like a racer... but nobody has said how that's done. :-)

From a racer, you can try something like this (for your objectives). Training at an intensity around the level of intensity objectively measured as ~ 4mmol/l of blood lacate is the most efficient way of improving your general ability. Since you won't be doing a lab test you can estimate this level of intensity.

One way is to look at your average HR during a steady effort that is about as hard as you can go for 40-60 minutes. Nobody really wants to do that effort so try some intervals around your 160bpm (~80% of ACTUAL MHR) . 3 rep's for 6 minutes each with 4' rest between. Twice per week is fine for now. If you can't quite finish the third one around that HR then you probably need to set your target a bit lower next time. If that effort seems a bit too easy then try it a few beats higher next time. You'll learn about the pacing as you go. You should finish these intervals not exhausted, like you could do another half of one if you had to. You should be able to manage a one sentence conversation with the person next to you. So, not out of breath that you can't talk. This is key. If you try to do these too hard you'll plateau soon, just like you do if you listen to the spin class instrutors who think faster is better, and no pain/no gain.

Following week you add a minute or two to each interval. When you're up to doing 3 x 15' you'll be feeling much better. You can try some on a climb for even more effectiveness. If you are riding 5 days per week you can eventually do these 3 times per week. In a month or so you can come back and report on your progress, and then maybe you can introduce some other kinds of intervals that will help you and provide some variety. For now, there's no need for you to do intervals above your (4mmol/l) lactate threshold unless your weekly training time is limited to something below 5 hours.