Flat: Elegant, Victorian, stylishly decorated, high ceilings, spacious, clean, quiet.
Host: Santiago extremely welcoming, sociable, fluent English, fluent Spanish. Very helpful in suggesting places to see; provides free maps. Sympathetic to the travails of the "guiri" mindset.
Location: Centre of the Madrid. Less than 10 minutes walk to anywhere in the heart of the city.
Recommendation: highly recommended