Thank you to roseabi for suggesting this workout - I LOVED it! 
I loved it because the workout was simple to follow, adaptable and varied. To expand......
1. The exercises were straightforward, needed very little space and mostly standing. A little window popped up on screen to show what was happening next so I could be ready.
2. The exercises are a mixture of strength and flexibility and NO reps (I really find workouts with repeated exercises soooo boring and dare I say - 'repetitive'!!)
3. The workout alternated between an exercise and walking - both only 30 seconds, which kept me motivated.
4. The workout is adaptable - the walking sections can be 'on the spot', round the room, active marching or jogging. I jogged up and down the stairs! I made some of the exercises a little easier, for example push ups with knees on the floor.
4. The whole workout was only 14 minutes. I did it twice, the second time I used my Garmin to find out how far I had jogged (.76km).
By the end I sweating (the house was quite warm) and heart rate raised so I reckon a good workout! I am going to try the second workout in the series tomorrow.
PS I found this picture which suggests some other ways of getting up the stairs - the crouched walk looks hard! 
Intermediate workout 