We'd also would tie Madonna and Elvis for 9th most all time time. With era 8, we could tie MJ, Boyzone, and Cliff Richard.
U2: 19
28/04/1985 THE UNFORGETTABLE FIRE
22/03/1987 WITH OR WITHOUT YOU
28/05/1987 I STILL HAVEN'T FOUND WHAT I'M LOOKING FOR
27/08/1987 WHERE THE STREETS HAVE NO NAME
22/09/1988 DESIRE
06/04/1989 WHEN LOVE COMES TO TOWN*
15/06/1989 ALL I WANT IS YOU
25/10/1991 THE FLY
05/12/1991 MYSTERIOUS WAYS
29/02/1992 ONE
25/11/1993 STAY (FARAWAY, SO CLOSE)
08/06/1995 HOLD ME, THRILL ME, KISS ME, KILL ME
06/02/1997 DISCOTHEQUE
22/10/1998 SWEETEST THING
12/10/2000 BEAUTIFUL DAY
01/02/2001 STUCK IN A MOMENT YOU CAN'T GET OUT OF
19/07/2001 ELEVATION
11/11/2004 VERTIGO
10/11/2006 THE SAINTS ARE COMING **
* U2 with BB King
** U2 and Green Day
The Beatles: 13
10/05/1963 FROM ME TO YOU
30/03/1964 CAN'T BUY ME LOVE
20/07/1964 HARD DAY'S NIGHT
07/12/1964 I FEEL FINE
06/04/1965 TICKET TO RIDE (STRAIGHT IN AT NO. 1)
02/08/1965 HELP! (STRAIGHT IN AT NO. 1)
13/12/1965 DAY TRIPPER / WE CAN WORK IT OUT
20/06/1966 PAPERBACK WRITER (STRAIGHT IN AT NO. 1)
15/08/1966 YELLOW SUBMARINE
20/07/1967 ALL YOU NEED IS LOVE
14/09/1968 HEY JUDE (STRAIGHT IN AT NO. 1)
03/05/1969 GET BACK*
21/06/1969 BALLAD OF JOHN AND YOKO (STRAIGHT IN AT NO. 1)
* The Beatles with Billy Preston
Westlife: 13
01/04/1999 SWEAR IT AGAIN
12/08/1999 IF I LET YOU GO
21/10/1999 FLYING WITHOUT WINGS
16/12/1999 I HAVE A DREAM / SEASONS IN THE SUN
21/09/2000 AGAINST ALL ODDS *
02/11/2000 MY LOVE
08/03/2001 UPTOWN GIRL
08/11/2001 QUEEN OF MY HEART
07/11/2002 UNBREAKABLE
27/03/2003 TONIGHT
20/11/2003 MANDY
27/10/2005 YOU RAISE ME UP
17/11/2006 THE ROSE
* Westlife with Mariah Carey
ABBA: 12
18/04/1974 WATERLOO
15/01/1976 MAMMA MIA
01/04/1976 FERNANDO
27/08/1976 DANCING QUEEN
17/03/1977 KNOWING ME, KNOWING YOU
12/01/1978 TAKE A CHANCE ON ME
14/09/1978 SUMMER NIGHT CITY
01/02/1979 CHIQUITITA
21/10/1979 GIMME GIMME GIMME
16/08/1980 THE WINNER TAKES IT ALL
09/11/1980 SUPER TROUPER
06/12/1981 ONE OF US
Cliff Richard: 9
28/12/1962 BACHELOR BOY / NEXT TIME
27/05/1963 LUCKY LIPS
25/11/1963 DON'T TALK TO HIM
06/04/1968 CONGRATULATIONS
12/06/1970 GOODBYE SAM HELLO SAMANTHA
12/08/1979 WE DON'T TALK ANYMORE
12/10/1986 ALL I ASK OF YOU *
20/03/1986 LIVING DOLL **
24/11/1988 MISTLETOE AND WINE
* Cliff Richard with Sarah Brightman
** Cliff Richard with the Young Ones featuring Hank B Marvin
Michael Jackson: 9
31/05/1981 ONE DAY IN MY LIFE
06/02/1983 BILLIE JEAN
30/07/1987 I JUST CAN'T STOP LOVING YOU*
17/09/1987 BAD
26/11/1987 THE WAY YOU MAKE ME FEEL
16/02/1989 LEAVE ME ALONE
06/07/1989 LIBERIAN GIRL
14/11/1991 BLACK OR WHITE
24/08/1995 YOU ARE NOT ALONE
* Michael Jackson with Siedah Garrett
Boyzone: 9
06/10/1994 LOVE ME FOR A REASON
20/04/1995 KEY TO MY LIFE
03/08/1995 SO GOOD
16/11/1995 FATHER AND SON
10/10/1996 WORDS
23/04/1998 ALL THAT I NEED
06/08/1998 NO MATTER WHAT
25/11/1999 EVERY DAY I LOVE YOU
05/03/2010 GAVE IT ALL AWAY
Dickie Rock & Miami: 8
09/12/1963 THERE'S ALWAYS ME
11/05/1964 I'M YOURS
19/10/1964 FROM THE CANDY STORE ON THE CORNER
24/05/1965 EVERY STEP OF THE WAY
08/11/1965 WISHING IT WAS YOU
21/02/1966 COME BACK TO STAY
20/04/1968 SIMON SAYS
26/05/1977 BACK HOME*
* Dickie Rock Solo
Elvis Presley: 8
01/10/1962 SHE'S NOT YOU
10/12/1962 RETURN TO SENDER
15/07/1963 DEVIL DISGUISE
14/06/1965 CRYING IN THE CHAPEL
05/07/1969 IN THE GHETTO
16/07/1970 THE WONDER OF YOU
01/09/1977 WAY DOWN
13/06/2002 A LITTLE LESS CONVERSATION *
* Elvis Presley vs JXL
http://www.irishcharts.ie/facts/most_no1s.htm
Madonna: 8
18/07/1985 INTO THE GROOVE
23/01/1986 BORDERLINE
19/06/1986 PAPA DON'T PREACH
28/09/1986 TRUE BLUE
09/07/1987 WHO'S THAT GIRL
09/03/1989 LIKE A PRAYER
13/11/2003 ME AGAINST THE MUSIC *
16/05/2008 4 MINUTES **
* Madonna with Britney Spears
** Madonna featuring Justin Timberlake
Dustin: 7
13/12/1990 THE CHRISTMAS NO. 1 *
10/11/1994 SPANISH LADY **
07/11/1996 RAT TRAP ***
13/11/1997 GOOD LOOKING WOMAN ****
18/11/1999 32 COUNTIES
22/11/2001 SWEET CAROLINE
16/05/2002 HERE COME THE GOOD TIMES *****
* Dustin and Zig and Zag
** Dustin and Ronnie Drew
*** Dustin and Bob Geldof
**** Dustin and Joe Dolan
***** Dustin and the Irish World Cup Squad
Britney Spears : 7
20/02/1999 BABY ONE MORE TIME
22/01/2000 BORN TO MAKE YOU HAPPY
15/11/2003 ME AGAINST THE MUSIC*
04/03/2004 TOXIC
17/06/2004 EVERYTIME
04/11/2004 MY PREROGATIVE
10/01/2008 PIECE OF ME
* Britney Spears featuring Madonna
I'm excited 
