I don't know much about the ipad, but on my emails I highlight the first one, then press the shift key and highlight the last one I want to delete - that highlights all the ones in between, I can then press Delete.
On mine, I go to inbox, then click on edit and select all the ones I want to delete. Then I click 'move' and send them to trash and then empty the trash (I have only just discovered how to do this, I expect there is a much quicker way).
Thanks sherrardk,but still has to be done individually but,might be the quickest way.boxtops,I should have said you can't access the Keyboard when in Email mode but thanks for your help anyway.