I tried the cycling to work, and found I could make it work for me on a 6 mile or so, 30 minute cycle, twice a week. My bike was slow, and I wasn't particularly fit.
Incidentally, I did try the going slower thing, but I don't know if it's Manchester's humidity but it didn't really make much difference! (This could have been that my mountain bike's gear were irrepairably stuck in top gear - least this city is flat!)
In theory, I'd also found a way around the sweat problem. A new gym opened around the corner from work, and had a special offer of £10 a month. I sold it to myself, that it was worth just to have a shower when I got to work - and I'd not have one before I left in the morning. As a bonus, it was a gym, and they're kinda full of fitness gear, so I managed to overcome my pretty entrenched fear of these gym place and booked a trainer to give me a personal training plan. I'd say it's beat my fear of gym's and 'that' kind! Anyways I'm sure this story may one day go on to to say I lost 50lb - I'd be happy with 1 stone tbh, but that job ended and now I'll be working much closer to home.... a 10 minute cycle / bus journey. So, a bit less exercise, but less faff.
Still hoping that one day I can buy a house, with a similar commute from work. Though my generation (mid-30s) is still priced out of the housing here unless you're in a couple, both on decent incomes. That's definitely changing though!!