Having installed secondary double glazing and reduced about 99% of draughts around the windows and improved the overall room temperature by around 2C, I would be interested to know if anyone has had their external walls insulated and if so what have been the benefits?

The problem in Spain is that 'most' houses are not built with cavity walls.

The bricks themselves have holes in them and that's about it.

It may be that the more modern house are now built with cavities but I wouldn't know.

The other issue is that if you put extra insulation on the inside (with expanded polystyrene coated plasterboard for example) then the walls will not be able to breath properly and with no damp proof course, this may be an issue.

I think it's normal now. We built our house 10 years ago and the outside walls were sprayed on the inside with foam and then the second wall built inside that one. That way you get the foam insulation and another air gap.

It also seems normal to spray the roof externally before tiling it. Our roof is actually constructed of interlocking sandwich boards with 10cm of polystyrene insulation between them.

Building standards in Spain have improved enormously in the last 15 years particularly with regards to insulation.

Yep, I can believe that. When we reformed one of our properties, we used the polystyrene sprayed onto the roof - great stuff for insulation but also for strength.

Our walls are solid concrete panels about 10cm thick so get very cold in winter and allow heat to escape. I was thinking about this type of insulation:

http://www.eco-villas-in-spain.com/e...insulation.php

That is very similar to a system that has been used in the Uk on many, mainly council estates, that were built in the days when pre-cast concrete construction was common and later needed better insulation.
You need to ensure that any any stop/angle beads used when rendering are stainless steel not galvanised to prevent problems later (rust staining)

are they really precast panels? or is it concrete blocks / red bricks with a concrete render?.
drywall may be better solution. rather depends if moisture [damp] is evident to determine best insulation

in the past 10 the buildings were done bit better that be4, doesn´t really mean the best way (including insulation) - normally insulation issue very poor in Spain´s building, unless some particularly ; th eonly thing every builder has looked over was to do it fast and cheap, as demand was very high