Replace the trunk prefix 0 with country code +44, including the plus symbol.
(The plus sign means "insert your international access prefix here." From a GSM mobile phone, you can enter the number in full international format, starting with the plus sign. The most common prefix is 00, but North America (USA, Canada, etc.) uses 011, Japan uses 010, Australia uses 0011, and many other countries use different prefixes.)
If it's a UK mobile that just happens to be in Spain, dial the UK number as normal. The physical location of the mobile does not affect how you dial its number.
If you are calling a Spanish mobile phone, prefix the 9-digit Spanish telephone number with +34 (calling from a mobile) or 00 34 (otherwise).
The most reliable way to place such a call is to put the number in international format. Replace the leading 0 of the UK number with country code +44, including the plus symbol.
(The plus sign means "insert your international access prefix here." From a GSM mobile phone, you can enter the number in full international format, starting with the plus sign. The most common prefix is 00, but North America (USA, Canada, etc.) uses 011, Japan uses 010, Australia uses 0011, and many other countries use different prefixes.)
If you are in Spain, using a UK mobile phone to call a telephone number in Spain, the most reliable method is to enter the number in full international format, beginning with the telephone country code (+34 for Spain), including the plus symbol.
To call a UK mobile (or any other UK number) from a Spanish mobile, just replace the trunk prefix 0 at the beginning of the UK number with country code +44, including the plus symbol. For example, 07700 900123 becomes +44 7700 900123.
UK mobile numbers are in the range +44 7400 through +44 7999, with six further digits for the full number.
Note that it does not matter if the UK mobile is in the UK, in Spain, or in some other country.
(The plus sign means "insert your international access prefix here." From a GSM mobile phone, you can enter the number in full international format, starting with the plus sign. The most common prefix is 00, but North America (USA, Canada, etc.) uses 011, Japan uses 010, Australia uses 0011, and many other countries use different prefixes.)
To call a UK mobile from Spain, replace the leading 0 of the UK mobile number with telephone country code +44.
To call a Spanish mobile that happens to be physically located in the UK, dial the Spanish mobile number exactly the same way you do when the mobile is in Spain.
(The plus sign means "insert your international access prefix here." From a GSM mobile phone, you can enter the number in full international format, starting with the plus sign. The most common prefix is 00, but North America (USA, Canada, etc.) uses 011, Japan uses 010, Australia uses 0011, and many other countries use different prefixes.)
0044 and then the number but omit the first '0'.
It makes no difference where the phone is currently located. Just dial the normal number and the network will re-route the call as necessary.
00 34 and then the Spanish mobile number.
+34 (including the plus symbol) followed by the 9-digit Spanish number
Enter the country code for Spain, +34, followed by the Spanish mobile number. If your mobile doesn't allow you to enter numbers in international format, substitute the 00 prefix for the plus sign.
The telephone country code for Spain is +34, followed by the 9-digit Spanish domestic telephone number. If you are calling on a GSM mobile phone, or most other types of mobile phone, you can enter the number in international format, beginning with +34 (including the plus symbol). Otherwise, substitute the appropriate international access prefix (dependent on your current location, not on the number you are calling) for the plus symbol. The most commonly used prefix is 00, but many countries use other prefixes, and some have multiple prefixes for specific types of international calls.
Spain
Spain is country code +34. From Ireland, dial 00 34, followed by the 9-digit Spanish number.(The plus sign means "insert your international access prefix here." From a GSM mobile phone, you can enter the number in full international format, starting with the plus sign. The most common prefix is 00, but North America (USA, Canada, etc.) uses 011, Japan uses 010, Australia uses 0011, and many other countries use different prefixes.)
If you're calling a UK mobile that is physically in Spain, just dial the UK mobile number. It does not matter where the mobile is physically located. If you're calling a Spanish mobile, dial 00 (the prefix for outbound international calls from the UK), then 34 (the country code for Spain), and then the 9-digit Spanish mobile number. If you're calling from a GSM mobile phone, you can dial +34 (including the plus symbol) instead of 00 34.
To make a call to any number in the United States from anywhere in Spain one would dial 00 + 1 + U.S. Area Code + 7-digit Phone Number. It is the same if calling a U.S. mobile number-- 00 + 1 + 10 digit cell number (including area code).
Lanzarote is in Spain, which is country code +34, dialed from Ireland as 00 34. The rest of the number should be 9 digits. Most landline numbers in Lanzarote begin with +34 928.(The plus sign means "insert your international access prefix here." From a GSM mobile phone, you can enter the number in full international format, starting with the plus sign. The most common prefix is 00, but North America (USA, Canada, etc.) uses 011, and many other countries use different prefixes.)
To ring a Spanish mobile phone (anywhere in the world that it may be physically located), you dial your international access prefix (most commonly 00, or use the plus sign on a GSM mobile), followed by country code 34 for Spain, and then the 9-digit Spanish number. To ring a mobile from some other country that happens to be physically in Spain, dial the number exactly the same way you would if it were in its home country.
Since 2007, calls from Spain to Gibraltar must be dialed using the full international format. From a GSM mobile phone, dial +350 and then the subscriber number; from a landline, dial 00 350 and the subscriber number.
00 34 plus the full Spanish number.