I've been doing a 16 - 18 hour break. Last week on 5:2 I had a 3lb loss, which for me - slow loser! - is a good number. On a 24/7 VLCD I only tended to lose that much.
I'm eating more like 1800 on non fast days but I'll review that if I lose less than 2lbs a week.
Fasting days for me have just been soup or salad or steamed veges, plus eggs or fish or a (small, kiddie sized!) piece of steak. When I looked at it, it kind of works out approx 100 cals from fat, 250 from protein, and 150 from veges.
Drinking lots of water. Had slight headaches and rumbly tummy the first week but it's got way easier.
Have a fab week 5:2ers!