Enecosse
The rules are, if you are a normal person, that you are non-resident, irrespective of other circumstances, if you go abroad to work full time. That your family stay put in UK is irrelevant to most people working full time abroad. It possibly does matter to us. My family are represented by an MP and they are potentially affected by this so I'm not really adding to UK ties by getting them involved as, if I did a normal job, it's your contract of employment not your ties to the UK that matter.
Lubeoil
They make it quite clear that any flight ex UK counts as a day of work and an inbound flight doesn't. You're allowed 20 days of work so no more than 20 UK flights per tax year.