The power here, as in the rest of Europe is a 'nominal' 230V, 50Hz (see http://users.metro2000.net/~purwinc/seec2_2.htm).  The UK used to be 240V but a few years ago they harmonised with the rest of Europe and now it's a 'nominal' 230V the same.

Most, if not all, equipment is rated 220/240V to work in the whole of Europe.

The difference here is that, unlike the UK, there is no standard for the connection of the phase and neutral wires in a socket.  In the majority of cases this isn't a problem as most equipment doesn't care as the circuit is designed for the European market.

There are exceptions however.  If you do have a piece of equipment that doesn't work as expected then (crazy as it sounds) it's worth turning the plug around and trying it - you may find it works.  You can buy replacement plugs here - there are two types - one has an earth connection, the other doesn't. Just use the type you need for whatever appliance you have.  

All plug sockets should have an earth. The older 2 pin sockets don't have an earth connection and shouldn't be installed in a new installation - if they are then it may well fail the electrical inspection and won't be allowed to connect  to the mains supply.

The exception is (sometimes) a UK TV - this will work ok with satellite systems, dvd's and so on but it won't necessarily work with the Spanish terrestrial TV signal - you'll get a picture but no sound.  This is due to the differences in the way the signal and sound are transmitted (for those interested in that sort of stuff the UK uses PAL I with an audio subcarrier of 6MHz and video bandwidth of 5.5MHz, Spain uses PAL G with an audio subcarrier of 5.5MHz and video bandwidth of 5MHz). The Video frequency doesn't cause a problem but the audio one does.  You may find that your video recorder is capable of receiving Spanish TV and can cope with the difference - if you connect it to the TV with a SCART cable then everything may work absolutely fine!

You mention about your dishwasher and water - actually dishwashers are much more efficient with water than many people believe.  The newer machines can actually use less water than washing up by hand and if you have an 'A' rated one then it's going to be energy efficient as well - so don't discount it!

Obviously what you bring/use will depend on the power you have available - be it mains or solar/generator.  Anything that generates heat (washing machine, dishwasher, iron, hairdryer, kettle, toaster etc.) will need a reasonably good supply.  It's worth getting the wiring checked out as the Spanish were a bit lax in their concept of power verses cable thickness - the worst I've seen has been an electric cooker (rated at 8KW) connected with bell wire (intended for use where power consumption is less than 50W) needless to say the results were impressive - the wire caught fire, vapourised and left a nice black carbon mark on the ceiling!

Nigel