To telephone Spain (including the Canary and Balearic Islands) from the UK dial 0034 followed by the appropriate area code (see below) and then the number. The area code plus the telephone number should be nine digits. Including the 0034 therefore, you will always need to dial a 13 digit number from the UK for any phone or fax in Spain.
Dial 0044 then the UK area code (without the initial 0) followed by the number. For example to telephone the London number 020-7654321 from Spain you would dial 0044-20-7654321.
Always dial the full 9 digit number (including the area code) even when calling from within the same area. If you are given a phone number that is less than 9 digits you will need to add the regional prefix (see the list above). Public telephone booths (locutorios) and street-corner telephones can be found throughout Spain. These take coins or phone cards which can be obtained from post-offices (estafeta de correos) and tobacconists (estancos). There are also central telephone offices (telefonicas) where you can make international calls and pay afterwards. Avoid using your hotel telephone as this is likely to be more expensive to use than a public phone.
Its very useful to have your own phone when on holiday. However remember that some mobile phones will not work abroad. Check with your provider before you go. Also find out about text messaging and how to get your voice messages, as this will almost certainly be different than at home. In particular find out about charges, it may cost more to use your phone abroad and you may have to pay to receive calls as well as make them!