Exactly when does residency begin??

It varies, David.

For the purposes of qualifying for the Convenio Especial, it's the day you take up residence here.

For tax purposes it's the date you register on the padrón.

For the TIE, the start date on mine is when I submitted the EX-23 to change from residency certificate for TIE.

For EX-20 applicants I don't know, but I'd guess it would be at the second stage of the process when you submit the EX-23.

Thanks Jim, 

I suppose I had better contact the UK Gov to find out when they recognise residency. We are applying soon but our house has not yet sold so I am holding back a bit. I understand we have until 31st December to apply and that Spain has some sort of extension until 30th June to sort everything out, I suppose that's if something is missing or not quite right it gives them breathing space. Let's hope the uk Gov accept an application in mid December for pension and health, but I'm not holding my breath

"For the TIE, the start date on mine is when I submitted the EX-23 to change from residency certificate for TIE"

So how does that tie in (no pun intended) with time served towards 5 years residency for permanent residence? 

Does anyone know the date/stage of the residency application process that the UK Gov use to establish you are a Spanish resident in order to maintain pension and health care??

It doesn't matter.

Ask for an Si from the NHS BSA, then take it to INSS to register for healthcare.

Notify DWP re the change of address for your pension, and give them the details of your bank account if you want the pension paying here.

 The only problem is I'm currently only 63 so I cant get an S1 and don't get the state pension yet

You'd better ask Ray. My TIE is for permanent residency.

In that case you'll need private health insurance.

Don't waste your time asking anyone in the UK - that won't do anything for you.

I know what I need to obtain residency I just needed to know when the residency starts in the eye of the UK gov, Padron, application date, finger print date, TIE collection date or some other date?