Performing a Case calculation to return a range of numbers

I am using a Case calculation in a Calculation field type and it is not working correctly. When a particular Centre is selected from a drop down list, I want to return a number of Centre ID depending on centre selected. My calculation is as follows:

Case ( Centre="Armidale Minimbah"; 25;
Centre="Ballina"; 1;
Centre="Barrack Heights"; 3;
Centre="Bega Bandara"; 2;
Centre="Bellambi Point"; 4;
Centre="Berkeley Noogaleek"; 29;
Centre="Brewarrina"; 5;
Centre="Broken Hill"; 6;
Centre="Corrimal"; 8;
Centre="Corrimal East KU"; 22;
Centre="Doonside Ngallu Wal"; 27;
Centre="Dubbo West"; 12;  
Centre="Eden"; 13;
Centre="Griffith Dorothy Waide"; 11;
Centre="Gunnedah Winanga-Li"; 40;
Centre="Jervis Bay"; 16;
Centre="Kempsey Dalaigur"; 10;
Centre="Koonawarra"; 21;  
Centre="Lightning Ridge"; 23;
Centre="Lismore Jarjum"; 15;
Centre="Minto Waranwarin"; 37;
Centre="Moruya Northside"; 30;
Centre="Mount Druitt Yenu Allowah"; 41;
Centre="Narrabri West"; 26;
Centre="Nowra East Clipper Road"; 7;
Centre="Nowra East Cullunghutti"; 9;
Centre="Queanbeyan South"; 31;
Centre="Sanctuary Point"; 32;
Centre="Sanctuary Point The Basin"; 35;
Centre="Toronto Nikinpa"; 28;
Centre="Tweed Heads South"; 36;
Centre="Wagga Wagga Kingfisher"; 19;
Centre="Walgett Koolyangarra"; 20;
Centre="Wallaga Lake Little Yuin"; 24;
Centre="Warrawong Community"; 38;
Centre="Warrawong South Coast"; 33;
Centre="Wilcannia Barlu Kurli"; 39;
Centre="Wollongong Kids Uni North"; 17;
Centre="Wollongong Kids Uni South"; 18;
Centre="Wollongong South Coast Workers"; 34;
Centre="Wreck Bay Gudjahgahmiamia"; 14;
"Other")

The following centres return the correct number:

Armidale Minimbah, Ballina, Barrack Heights, Bega Bandara, Bellambi Point, Doonside Ngallu Wal, Moruya Northside, Warrawong Community, Warrawong South Coast, Wilcannia Barlu Kurli, Wollongong Kids Uni North, Wollongong Kids Uni South, Wollongong South Coast Workers, Wreck Bay Gudjahgahmiamia.

The remaining centres return "other" upon selecting them. I can't figure out why the others are not returning their assigned number! Have double checked the spelling and can't see any problems.

Any help would be gratefully accepted!

Penny