Hi miss piggy,
I have my eye on a cyclo-cross bike at the moment that I want to use for a daily commuter "a kona jake the snake"
Sounds like you are getting enough slow steady pace stuff so I would look at HIT sprints, try hill either on the bike or running, I have also been doing some tempo riding, 2 to 5 mins flat out, 10 mins slow, repeat as many times as you can up to 1 hour.
I am no expert but would look at doing more HIT workouts targeting the legs try for a 40-45 seconds of work 15 seconds rest repeat for 10 to 15 minutes. I would look at 3 compond exercises starting on the minute each minute for the allocated time. Try doing squats, push ups or pull ups then dragon lunges ( some times called ice skaters) or hindu squats. This works the legs then the upper body then back to the legs which gets the blood flowing from lower body to upper body. Play around with reps so you work for that 40-45 secs then have 20-15 secs rest before starting again ( each minute on the minute)
Another one I like is as many rounds as possible in 20 mins of:
A1: 10 reverse lunges ( alt legs)
A2: 8 reps of let me ins ( horizontal rows) works the quads as well as the arms
A3: 6 push ups
I followed this up with 9 mins of 10 deadlifts/ sumo squats, 10 kettle bell swings followed by 3 pull ups every minute on the minute as above the other day and that got the heart rate right up there....
Finish off with 4-5 minutes of planks to strengthen the core.
"Times fun when you are having Flies" Kermit the frog