It varies a lot week to week. And I would guess provider to provider too. In an average week, I have 6 hours of class and probably spend an average of 15 hours outside class on homework. More at assessment time, of course, and less in some other weeks. My classmates mainly seem to spend a lot less time than this, but I think it shows in the results 
The BPP part time programme is on weekends. So once a month you have about 16 hours of class in a weekend. The preparation for those classes is spread over the rest of the month.
Personally, I prefer the regular contact at City over the monthly approach at BPP, so I would choose Northumbria on that basis, but I realise this is a personal decision and comes down to how you learn best and how the rest of your life is structured. With a PhD rather than a full time job, you might be able to blitz the prep work in the week before the study weekend by ignoring your PhD for that week and then return to the PhD for the three weeks after the study weekend before you go into BPTC overdrive again.
