If you have internet banking it's really easy but you do have to have it set up before hand. We had to get the EBAN and SWIFT numbers from our PP bank, the UK bank then give you a security number which has to be posted to you, once it is all set up it only takes a few minutes to do the transfer and the money is usually in your Spanish account within the hour .
I've used some foreign exchange companies like FirstFX and that worked well. You set up your details with them and as & when you need to transfer money over to your PP bank, you just ring them and transfer the funds from your UK account to them. Generally no additional fees and a pretty competitive rate.
I also use the direct transfer system available between Halifax bank in the UK and Lloyds Bank International. Once you have that set up you can transfer money between your accounts on your home computer. It's just a shame that the Banco Halifax branch in PP has closed though and the nearest branch is now in Santa Ponsa or in Palma for Lloyds.
Smiddy,
I normally use RBS Internet banking, not sure if it's the best way to do it but it is easy. RBS charge £10 and transfer at whatever is the RBS exchange rate that day.