Kev asked:
"How many need to be sold to get to 115?"
At least 1 and no more than 15 I would guess
BTW, according to
en.wikipedia.org/wiki/UK_Singles_Chart
the Gorillaz reacted against the chart rule (downloads are only counted if there is also a physical releases)
last year with a limited edition of 300:
"This new chart rule was controversial and - to highlight it - Gorillaz released 300 copies of their single Feel Good Inc. on April 12 2005, a month before its general release. This allowed it to chart at 22 and remain in the top 40 for a longer period."