Wow, I've just finished VTCT IHM and we were taught a 20 min routine, but it seems the norm is quite a bit longer.
For my case studies (done mobile) I allowed about 35 mins from in the house to out again, apart from the first which was about an hour in total due to consultation.
There are a few movements in the routine I was taught that I'm not comfortable doing, so plan to change things a bit.