re: the cycling/swimming/other activities
the general consensus on LL is as follows:
If you were doing some exercise before, then you will be fine to continue doing that exercise as your body is used to it.
If you were not doing any exercise before, it's best not to start while on the VLCD.
You body is going through enough as it is, without adding further strain to it by asking it to things it would (technically) not be fit enough to do even while eating healthily, let alone with <550cals a day
In my case, ever since I started walking/running home from work (around 4.5miles) my losses each week have dropped by 50%, from 5-6lbs a week to 2-3lbs, with a STS last week, and I feel hungrier all the time as well.
Of course, I can only speak from a personal point of view, but for me, the exercise cutting my losses isn't a deterrant - I would rather abstain for longer and enjoy exercise than sit around watching DVDs every night, bored and feeling like I should be doing more.
but that's just me.
Bottom line, listen to your body - if it tells you to take it easy, then take it easy, no matter how long you feel like you need to