Do I need residency to stay upto 6 months?

If you are from the UK then you can spend a maximum of 90 days here in a rolling 180 without applying for Residency. If you spend more than 183 days you become a tax resident. Owning a home makes no difference and after December 31st your passport will be scanned on entry and exit and if you overstay you risk at least a fine and possibly a restriction on returning.
The 90 days include all trips within the Schengen zone.

It was always 90 days in any 180 only from Jan 1st. they will be checking and where necessary enforcing it. 

thanks everyone

what if I apply for residency, how will this effect me in the future when I am eligible for my state pension (another 10 yrs yet)

I am not sure what the benefits of residency are besides being able to stay longer than 90 days, which I would like to do.

I will not be working in Spain, our income will be from savings and a small income from renting out our home in the UK.

if you are resident here in spain and say go to france can you only stay in france 90 days or is this just for people who live in the uk many thanks

"I will not be working in Spain, our income will be from savings and a small income from renting out our home in the UK"

I doubt if you will be able to meet the financial requirements to achieve residency. 

Steve 

If you gain Residency this year, you will qualify for free healthcare in Spain from age 66.

If you gain Residency after the end of this year you will have to pay for healthcare (assuming that you have the resources to qualify for Residency).

If you live to 86, the difference is around 40K Euros each. A big upside.

The downside ?   To retain Residency, you have to be in Spain for at least 6 months per year. You will be a Spanish Tax-Resident. You may have to pay more income tax in Spain (depending on your personal circumstances). 

thanks for this information, it is most helpful.

Would both my husband and myself need to have the 900 euro a month going in to our account or 9000 each in savings?

thanks