We have found to our cost
I once heard it said that anyone that has done some DIY in the U.K. instantly becomes a builder when they land in Malaga. So beware.
Finding a fair trading expat tradesman can be quite a challange nearly all try to charge U.K. rates and some are not really what they say they are.
If you are looking for a builder or plumber or the like, always make a point of asking for referances from other jobs they have done, and speak to local people before employing them.
The Spanish traders can be just as bad. Once they know that you are from the U.K. they see and they will put up the price.
Always get at least two quotes for any work you need done, and don't be afraid to haggle.
To be fair there are some honest people out there, it's finding them.
Good luck.