Outside lights
 

Could anyone please give me any information on the wiring needed for 20 watt outside lights many thanks.

Re: Outside lights
 

Exactly the same as any other lights - live, neutral and earth.

For outside wiring, the wires must be in conduit if some sort (metal, rigid plastic or the normal corrugated plastic).

Re: Outside lights
 

And if the conduit is any length at all, you'll find it much easier to thread the wires through (because in Spain the practice is to use individual wires; not a three-core cable) using a fish tape or a nylon equivalent.
Also don't forget that you'll need to use waterproof, external grade fittings to keep the rain out - otherwise the conduits could fill up with water and the lights could become "live".

Re: Outside lights
 

And of course don't forget that the indiviudal coloured wires are really expensive compared to the UK's twin and earth system. For instance I took out with us last year a 50metre reel of 1.5mm twin and earth cable. It was cheaper than a single 50metre reel of 1.5mm cable, be that live neutral or the earth in Spain.
So I am happier with the way our garden is wired, it has twin and earth which is sheathed itself running inside plastic conduit in our garden, extra protection over the Spanish system.