Darlington Borough Council - Statement from Darlington Borough Council regarding missing name from ballot paper

'A spokesperson for Darlington Borough Council said that voting in the general and local elections was continuing as normal in Darlington but that the name of one candidate, David Hodgson (UKIP)  had been missed off  ballot papers issued to one polling station in the borough. 

Approximately  89 ballot papers (0.1% of the total number of ballot papers printed)  had been issued, but as  soon as the issue was identified, corrected ballot papers were issued to the polling station concerned.'

More here

Questions that come to mind:
 

What happens to the votes of the 89 voters who were given the incorrect ballot paper?

Should they be asked to vote against?

What if they might have voted UKIP had there been a UKIP candidate on the ballot paper?

How were two different types of ballot papers printed: one with UKIP and one without?