Hi Donna
Yes, we have installed a spiral
It is a lengthy process!
First you must employ an architect, who will tell you firstly if it is possible
Without knowing exactly where you intend installing it, it is hard to give you the right advice.
Ours was an internal construction, going from our lounge, through the ceiling, entering our solarium above.
We employed a Spanish builder who had worked on the construction of our building, so he knew what he was doing!
We bought a kit form spiral from a Spanish builders supplier, but it would have been much cheaper to buy the same spiral via a UK company and have it delivered in Spain (You live & learn!)
If your architect gives the go ahead, you will pay to have plans drawn up
these will the be submitted to the Town Hall for approval
If you are on a community, you will need to inform them of your plans, also you will need permission from your nearest neighbour that it could affect.
If the Town Hall approves your plan, they will ask for a returnable warranty and provide you with a building licence.
Then the work can start.
This warranty money will only be returned after the work is done and the architect has inspected the work.
They will then put a certificate to the town hall to say the work has been done to plan and no damage to communial property has been caused.
If these criteria are not met, then the town Hall can keep your money to pay compensation to your community or your neighbour.
As for cost, its not cheap, don't think you can do it for 1 or 2 thousand Euro.
I have a breakdown somewhere, so would have to dig it out if you need further info.
hope this helps.