Freeing up space on iPhone

I had 1 Gb free on my iphone and wanted to free up some space. I deleted a large number of apps which added to over 2Gb in Apps (this was calculated using the figures of the data for each App under the Apps tab in iTunes). After deleting all of them the iPhone is only showing 1.2Gb of free space. I have tried restarting the iPhone and my computer and it makes no difference. I have confirmed the 15 apps I had deleted are gone. What is going on here? How do I free up the space?