| M | England |
| MC | Wales |
| MD | Isle of Man |
| MH | Jersey (clubs) |
| MI | Northern Ireland |
| MJ | Jersey |
| MM | Scotland |
| MN | Northern Ireland (clubs) |
| MP | Guernsey & Dependencies |
| MS | Scotland (Clubs) |
| MT | Isle Of Man (Clubs) |
| MU | Guernsey & Dependencies |
| MW | Wales |
| MX | England (Clubs) |
| MZ | Amateur stations (Shetland) |