BM rMMBMMa2S,
                                                               MM;        :: SM
                                                              M7             M
                                                              M           ;MMi
                                                          :MM8i        MMM@
                                                          M          MM            _______Scotland
      Atlantic Ocean                                     M.        ,MrM           /
                                                         iMM        MX2aMMWB:    /
                                                         ;M                 aMMMMMX
                                                        MM                         M
                                                       M                           M
                                                    iMMa                        . MM
                                                     M                         .M
                                                      MZMM;                    M
                                                        M                    :M
               Northern Ireland_________              a@                 .  MM
                                        \            ;8 MM              XMWM              North Sea
                                         \           M MM M,             M
                                          \          M2B 0MM        . iMMMM2
                                           \       :MM8  M  O        M
                                WMrM820B0   \     ;BM    M           O 0MMMM,
                              MB.    M8 MM  |     MW      M                WM
                           ;8@7    /MM MM@MMZMX         Ma                 _,M
                           WM;   _/           aM       M,                 |  MZ
                 ZMWMM        M /              M     rM                  _|   W,
               :SM    MMZ8 MMi |               M    ;M                 _-     7B
               MM         X     |             @M    0MMM WM:   MM;___-        M
                 MM             \   _____   O;2M    r  MM .MMr  MM.        O M
             ;MM7:               --/     \      M              MM          .   M
             M                            |  X M             .M               S2
              Mi                         X8WMS:              M                M
               MM:                      MSi                   M             .  MM
                 7MM                    M                     SM.MMM             MMX
               BMBSa                    M                       . B                M
              WM         Ireland        MS                       Ma                Z@
            2S    Z                    8r      Irish Sea        M            .       M
           MMMMMMMMi                   M                        M       . O           M
     :;0@WM       ;                    M                       M                      M
     @X88.                            MZ            :MMMMMMMMMMMO    O                i O
     8S88                            MW           SB; .      .:            O        MMMM a
    ;M                              M            Z0BMX       |                      M
      MMM                          M                ZM      /                        MM_________England
     i,MMM        7     MMM0MMMZ  M                 M       |                         M
       B0B.Bi. .:MMMMMMM2       MZW                 Mi      |   O                    MM
          r;ZBMW2                                 7Mr       |           O          0W
                                            :BMMMMS O       |                       MMrMMMMMMM
                                         MBMS               |                        B    O  MZ
                                         M    i             \      O                          M
                                         ,MMMMXM    O        |                                M,
                                               MZMMZ         |                       O        M
                               Wales__________/    M    O  @M                               O 2M
   Atlantic Ocean                                   Mi MMBMM2O          O                   ia
                                               S@Z    ;  M@                              XMM2
                                            SMMi ;@MMMMMM                              ZaM
                                          8MS                             .    ___   XMi
                                       .MMi                                   /Lon\ M
                                     MMS         .                O           \don/ M ar
                                 rBMM   MZ, O     MX8ZSMM          i                  . SM
                                rM   MMM  .MM@   M       MWMiMMMMMMMMMX                MZW
                                  2MM         M@M           XM        WMMMMMMM0aiXMMMMM.
                                                         English Channel

This omits any territories outside of the British Isles. (Also, as a note, Ireland is not a part of the UK; it's only on the map nominally, without any linked cities, for not-making-it-look-funny purposes.)

Made with ASCII Generator Public Beta 13, the E2 Offline Scratchpad, and far too much spare time.

Not being a UK resident, I'm not completely familiar with its every geographic facet, so if there are any errors here, or if you disagree with my scheme for which cities get the . and which get the O, or if you want me to add your favorite town/mountain/island/county line, message me. I thought about submitting this as Everyone, but I. . .uh. . .didn't want to give up the credit.