Have you heard of the 'Mediterranean Garden Society' (MGS) http://www.mediterraneangardensociety.org/ ;

It is a group who are interested in Mediterranean plants and having gardens that need very little water.  There is a Catalunya branch that is becoming active in this area, previously their activity was mainly in the north.

It is a society with members all over the world, they go on trips to various gardens and countries and have many experts in their membership.

If you are interested then give Brian Constable a call, 977059020 as he has been a member for many years and is trying to build interest in this area, he lives near L'Ampolla.

Many of the plants you'll find in garden centres are completely unsuitable for this climate, as will be almost anything that you bring from the UK.

One extremely well known garden centre that specialises in Mediterranean plants for dry gardens is Pépinière Filippi
(http://www.jardin-sec.com/). Also have a look at http://www.digthedirt.com/contributions/7131-The-Gardens-of-Olivier-Filippi-The-Driest-Gardens-on-Earth-, now wouldn't you like your garden to look like that, and not a drop of irregation in sight!