Questions about split year application

Hi, I'm current on a casual contract working part time in the UK. The contract end date is in Septebmer but I foresee no more work going on in early August. At the same time I've got an overseas full-time job offer; I'm planning to head for it overseas in late July and stay overseas for a couple of years. If I'm leaving the UK to take up the full-time position overseas, I believe I'll satisfy case 1 for split year application, but there are a few points I'm still unsure of. 1. Does my casual contract in the UK matter with my calculation of when my overseas part of the split year starts? 2. If the casual contract is irrelevant, do I start counting the reference period the first day I work for >3 hours overseas? 3. I'm currently in self assessment; am I right that I need not report any overseas income for the overseas part of the split year? 4. As I'm expecting to spend at least several years overseas, how do I inform the HMRC of that, and when should I inform the HMRC? 5. Can I opt out of self assessment, and if so, should I do that any time in the same tax year when I leave for overseas, or as soon as I leave for overseas? Thank you.

Hi G,
If you qualify for split year then you only report any foreign income for the UK part of the year RDRM12000 - Residence: The SRT: Split year treatment.
If you do not qualify then you will need to report all your foreign income to the UK Tax on foreign income.  
The guidance at RDRM12150 - Residence: The SRT: Split year treatment: Case 4: Starting to have a home in the UK only will help you work out if split year treatment applies. 
You can notify HMRC that you have left by completing a form P85 and this will also determine if self assessment is still required - Tax if you leave the UK to live abroad.
Thank you.