To call any UK number from Morocco, replace the leading 0 of the UK number with 00 44, or with +44 on a GSM mobile phone.
(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.)
Vodaphone
To call a UK mobile from a UK landline, you always just dial the UK mobile number, exactly the same way you do when it is in the UK. The network will find the mobile automatically, and the mobile user will pay any applicable surcharges for international roaming.
Just as you would call an English landline.
MOROCCO
You dial the normal number. The phone network will handling routeing the call to wherever in the world the mobile currently is.
Just dial the UK mobile number. It does not matter that the mobile is roaming in Ireland (or anywhere else); the network will automatically locate the mobile, and the roaming mobile user will pay any applicable roaming surcharges.
Dial 0044 (the country code for the UK) - then the mobile number WITHOUT the leading zero.
A Moroccan.
Where the UK mobile number is 07xxx xxxxxx dial either +44 7xxx xxxxxx or 00 44 7xxx xxxxxx. It doesn't matter which country the other phone is being used in.
+34 (including the plus symbol) followed by the 9-digit Spanish number
Morocco
Dial the UK mobile number in full international format: replace the trunk prefix 0 with telephone country code +44 (including the plus symbol).