I'm spanish, maybe moving to Tenerife (various questions)

I live in the UK and I might be moving to Tenerife with my mum. I was born there and I speak spanish but I've been living in the UK most of my life. I have a spanish passport only, I don't have a UK passport, and I've never lived in my own country except when I was very young. I went to school near Los Cristianos briefly. 

I'm doing my own research as well as asking on here, but getting some answers on a forum might save me some time. I have a few questions, so if anyone can help with any of these I would appreciate it. 


* I would like to work from home, online. I already do this sporadically, and I have a business bank account in the UK, and I'm a sole trader. 

If I manage to do some work online over there (i.e. teaching english or whatever), and set up a bank account there, could I just continue using my UK business account, be self employed in the UK, deal with HMRC as usual, and then pay myself into my spanish account? Would I be considered self employed over there? 

* If I do have to register as self employed in Spain, how would I do this?


* Apart from working from home, I'd also like to work in the many bars and restaurants that are all around. I have experience, and I speak both languages, so I guess that gives me an advantage in terms of getting work (but that's just a hunch - is it true?). 

What I'd like to do is have a casual arrangement with many establishments, and work either whenever they need an extra pair of hands or when I want to work. Nothing set in stone. Is it realistic to expect it to be as casual and informal as that? 


* Do I need an EHIC card or is it only really for people on holiday? 


* Are there any major differences between using banks and cash machines in Spain compared to the UK? 


* How do people pay for electicity, gas, water, etc? Also how do you set it up? If I was to live in one of those apartment buildings with amenities (i.e. pool) would it already be done? 


* How would I set up a landline and internet? 


* Stupid question : Can I take a UK iphone and cheap phone and get SIM cards for them there and use them without any issues? 

* There's something called empadronamiento, which I would need to do.If anyone knows about this, is this something I can do in the town hall? 

* Speaking of which, is the centro cultural de Los Cristianos effectively the same as a town hall? I know the actual town hall is up in Arona, but I've heard that many things can be done in the centro cultural and that Los Cristianos is becoming the main area for most things, inc. admin stuff. Can anyone clarify? 

* Where would I get a DNI? 

* Apart from the above, is there anything else I'd need to do to register my address? What if it's a temporary address (we'd be staying with my aunt at first)


* Where would I go to renew my passport? Town hall? Or is there some other place? 


* Where can I get an offline map of Tenerife for my computer? 


If you think you can help with any of these questions, I'd be very grateful. Thanks.