[Koha] Itemless records

[Deb Vincent]

Hi all
I have about 2000 bib records that I imported into Koha in the wrong 
format when I first started. I cleaned them from the reservoir, but they 
still appear when I do a catalogue search.
Is there any way I can stop them appearing? I have tried deleting in 
batches by their record number, but the records still appear in the 
catalogue. None of them have items attached - is there a way to delete 
itemless records?
Or is there something I need to do after deleting them to update the 
system?
Thanks for your help.
Deb Vincent