On |- class="vcard" | class="fn org" | Onchan | class="adr" | Isle of Man | class="note" | | class="note" | |- class="vcard" | class="fn org" | Onecote | class="adr" | Staffordshire | class="note" | | class="note" | |- class="vcard" | class="fn org" | Onehouse | class="adr" | Suffolk | class="note" | | class="note" | |- class="vcard" | class="fn org" | Onen | class="adr" | Sir Fynwy (Monmouthshire) | class="note" | | class="note" | |- class="vcard" | class="fn org" | Onesacre | class="adr" | Sheffield | class="note" | | class="note" | |- class="vcard" | class="fn org" | Onibury | class="adr" | Shropshire | class="note" | | class="note" | |- class="vcard" | class="fn org" | Onich | class="adr" | Highland | class="note" | | class="note" | |- class="vcard" | class="fn org" | Onllwyn | class="adr" | Castellnedd Phort Talbot (Neath Port Talbot) | class="note" | | class="note" | |- class="vcard" | class="fn org" | Onneley | class="adr" | Staffordshire | class="note" | | class="note" | |- class="vcard" | class="fn org" | Onslow Village | class="adr" | Surrey | class="note" | | class="note" | |- class="vcard" | class="fn org" | Onthank | class="adr" | East Ayrshire | class="note" | | class="note" | |} Op |- class="vcard" | class="fn org" | Openshaw | class="adr" | Manchester | class="note" | | class="note" | |- class="vcard" | class="fn org" | Openwoodgate | class="adr" | Derbyshire | class="note" | | class="note" | |- class="vcard" | class="fn org" | Opinan | class="adr" | Highland | class="note" | | class="note" | |} Or |- class="vcard" | class="fn org" | Oran | class="adr" | Moray | class="note" | | class="note" | |- class="vcard" | class="fn org" | Orange Row | class="adr" | Norfolk | class="note" | | class="note" | |- class="vcard" | class="fn org" | Oransaigh | class="adr" | Western Isles | class="note" | | class="note" | |- class="vcard" | class="fn org" | Orbiston | class="adr" | North Lanarkshire | class="note" | | class="note" | |- class="vcard" | class="fn org" | Orby | class="adr" | Lincolnshire | class="note" | | class="note" | |- class="vcard" | class="fn org" | Orchard Hill | class="adr" | Devon | class="note" | | class="note" | |- class="vcard" | class="fn org" | Orchard Park | class="adr" | Cambridgeshire | class="note" | | class="note" | |- class="vcard" | class="fn org" | Orchard Leigh | class="adr" | Buckinghamshire | class="note" | | class="note" | |- class="vcard" | class="fn