This is one possible solution.
You can create a custom property attached to servers called JDBC_URL.
Create smart groups for all UK servers and all IRL servers. For each group, right click & select Set Property for the JDBC_URL on all servers in the smart group.
Then the package can reference ??TARGET.JDBC_URL?? directly. This method will require maintenance for new servers or servers that change location.
And if LOCATION was a property class, then you might be able to use ??TARGET.LOCATION.DB_URL??