Sandi is the 47th biggest selling female of the 21st century for her debut single "I Wish I Was A Punk Rocker (with flowers in my hair)" according to the Official UK Charts Company. The full-list as of Jan 2009 can be found below:

1. Kylie Minogue - Can't get you out of my head (1100000)
2. Alexandra Burke - Hallelujah (1026830)
3. Atomic Kitten - Whole again (960000)
4. Leona Lewis - Bleeding love (937100)
5. Leona Lewis - A moment like this (845000)
6. All Saints - Pure shores (720000)
7. Sonique - It feels so good (650000)
8. Rihanna - Umbrella (628500)
9. Shakira - Whenever wherever (620000)
10. Girls Aloud - Sound of the underground (612000)
11. Las Ketchup - Asereje (The Ketchup Song) (590000)
12. Shakira ft Wyclef Jean - Hips don't lie (580000)
13. Spiller ft Sophie Ellis-Bextor - Groovejet (If this ain't love) (577000)
14. LeAnn Rimes - Can't fight the moonlight (570000)
15. Duffy - Mercy (556500)
16. Madonna - Hung up (525000)
17. Katy Perry - I kissed a girl (509050)
18. Pussycat Dolls ft Busta Rhymes - Don't Cha (500000)
19. Christina Aguilera, Lil' Kim, Pink & Mya - Lady Marmalade (480000)
20. Estelle ft Kanye West - American Boy (466100)
21. Gabrielle - Rise (457000)
22. Sugababes - About you now (455000)
23. Britney Spears - Oops… I did it again (445000)
24. Destiny's Child - Independent Women pt 1 (440000)
25. Leona Lewis - Run (435825)
26. Madonna ft Justin Timberlake - 4 minutes (432300)
27. Geri Halliwell - It's raining men (420000)
28. Sugababes - Push the button (410000)
29. Atomic Kitten - The tide is high (410000)
30. Beyonce - If I were a boy (409520)
31. Holly Valance - Kiss kiss (406000)
32. Melanie C & Lisa 'Left-eye' Lopes - Never be the same again (401000)
33. Madonna - Music (401000)
34. Girls Aloud - The Promise (399030)
35. Atomic Kitten - Eternal Flame (385000)
36. Pink - So what (384750)
37. Madonna - American Pie (382000)
38. Cheeky Girls - Cheeky song (touch my bum) (377000)
39. Katy Perry - Hot n cold (373900)
40. t.A.T.u. - All the things she said (370000)
41. Rihanna - Disturbia (367840)
42. Blu Cantrell ft Sean Paul - Breathe (365000)
43. Nelly Furtado - Maneater (361000)
44. Mariah Carey & Westlife - Against all odds (360000)
45. Melanie C - I turn to you (355000)
46. Beyonce - Crazy in love (355000)
47. Sandi Thom - I wish I was a punk rocker (350000)
48. Rihanna - Don't stop the music (344500)
49. Rihanna - Take a bow (336700)
50. Beyonce & Shakira - Beautiful Liar (335000)
51. Britney Spears - Toxic (330000)
52. Jordin Sparks ft Chris Brown - No air (329000)
53. Pink - Get this party started (325000)
54. Kate Nash - Foundations (320000)
55. Gabrielle - Out of reach (315000)
56. Madison Avenue - Don't call me baby (315000)
57. Anastacia - Left outside alone (310000)
58. The Corrs - Breathless (310000)
59. Britney Spears - Born to make you happy (307000)
60. Cascada - Everytime we touch (305000)
61. Gwen Stefani - Sweet Escape (300000)
62. Sophie Ellis-Bextor - Murder on the dancefloor (300000)
63. Michelle McManus - All this time (295000)
64. Dido - White Flag (294000)
65. Gabriella Cilmi - Sweet about me (290400)
66. Britney Spears - Womanizer (289100)
67. Sweet female attitude - Flowers (288000)
68. Adele - Chasing pavements (288000)
69. Destiny's Child - Lose my breath (285000)
70. Lily Allen - Smile (280000)
71. Rihanna - S.O.S. (Rescue me) (280000)
72. Christina Aguilera - Dirrty (280000)
73. Fergie - Big boys don't cry (275000)
74. Amy Winehouse - Rehab (275000)
75. Avril Lavigne - Girlfriend (270000)
76. Kylie Minogue - Spinning around (270000)
77. Sugababes - Freak like me (265000)
78. Destiny's Child - Survivor (265000)
79. Christina Aguilera - Beautiful (260000)
80. Rihanna - Unfaithful (255000)
81. Emma Bunton - What took you so long? (255000)
82. Geri Halliwell - Bag it up (255000)
83. Beyonce - Irreplaceable (255000)
84. Kelis - Milk Shake (250000)
85. Eve & Gwen Stefani - Let my blow ya mind (250000)
86. Samantha Mumba - Always come back to your love (250000)
87. Sugababes - Round round (250000)
88. Britney Spears - Everytime (250000)
89. Billie Piper - Day and night (245000)
90. Spice Girls - Holler / Let love lead the way (245000)
91. Lene Marlin - Sittin' down here (245000)
92. Frankee - Fuck you right back (245000)
93. Alicia Keys - No one (245000)
94. Girls Aloud - Call the shots (245000)
95. Samantha Mumba - Gotta tell you (245000)
96. Pink - Just like a pill (240000)
97. Shakira - Underneath your clothes (240000)
98. Mary Mary - Shackles (Praise you) (240000)
99. Pussycat Dolls - Stickwitu (235000)
100. Natasha Bedingfield - These words (235000)