If it is the 2005 Great Vic bike that you're using, you cannot slide the grips in any further - they are closed off at the outer end (at least the ones on mine are). You will have to buy new grips, however they are relatively inexpensive. When getting new grips, make sure they are open at both ends, so you can move them in enough to attatch the bar ends.
I havn't used hairspray, but have found that saliva workes a treat
Hair spray won't do any damage. If you don't use hair spray when attaching the new grips, they tend to twist on the handle bars which could be quite dangerous. My recommendation is to either trim back the existing grips to accomodate the bar ends, after moving the gear selector and/or brake handles to a comfortable position, or replace the grips with new ones, using hair spray. Either way, it's an easy, inexpensive job.
i have put them on i cut the ends off the grips and then used the allen key to lift the grip up a bit, i then sprayed some hair spray under the grip at both ends, the grips were then able to be slid along and attatched the bar ends
thanks for all your help!