How much Income? (Lima)

I am British, and am considering Retiring to Peru. I am married to a Peruvian. However, we will only be living on my Pension (currently £13,000).

Can anyone give me an idea of how much per year, you actually need to have a stress free retirement?

I like some idea, as I am trying to budget for £6,500, although it is not important if it is slightly more, the reason for the lower figure, is that would be the entitlement my wife would have, if anything happen to me.