Use the commute to do hiit training at starting from traffic lights, be safe though.
http://en.wikipedia.org/wiki/High-intensity_interval_training
I do it on my 10 mile each way commute untill I cant manage it anymore, it helps keeping a chocolate bar incase you get so wiped out you need a boost but that shouldnt happen very often.
It also makes a big difference eating properly although sometimes it dosent make sence for example after a week feeling really tired I felt really good on friday after eating junk and drinking beer the night before. I dont think supplements are bad but creatine seems a funny one to take by itself
Eating well for me on an ideal day goes like:
Oats
cycle
fruit
weights at gym
protine shake
nuts
raw salad, leafy greens brocolli pepperd, beetroot beansprouts+hemp oil
quinowa and roasted onion sweet potato galic peppers
protine shake
fruit
cycle home
flapjack
run or swim (only twice a week)
veg+quorn or beans or lentils
youl have to guess the times though but they are all spread out. Its quite a lot of effort not to give into the easy food option, normally by friday I fancy a pub lunch but without injuries I do 13+ hours training a week. Without eating like this I cant keep it up. And I do count commuting as training! Personally I dont think pasta and sandwiches cut it, at least they dont work for me. I think you should take every avaliable opputunity to avoid wheat as its the grain than appears in everything when you need a quick snack and have to buy something from the shop.
Its really important to stay hydrated too, I almost cant manage it without isotonic drinks
I also dont belive you have to do lots of long rides as I did a centry on my 3rd road ride last year (although it was a bit of a struggle on flat pedals) later on I also did 4 centurys in 4 days in a row when my previous training was only cycling to work for a max of 40 mins. My diet was strange then because I hardly ate anything but in both cases staying hydrated was really important for me as thats when I suffered and its really hard to get it hydrated again.
I find it hard to gague fitness improvements because if you try hard you always feel tired.
Phew long post, I think you can do it, its a great opputunity being able to commute if you sorted your diet and maybe joined a gym close to work and did some squats or deadlifts in the morning befor you shower you could really get somewhere with the fitness