I have built an app in HTML5. Can I upload the code to the PhoneGap build service and will they return it to me in a built state that can be transferred to the Apple app store or have I got the wrong end of the stick? Is there a cost involved if this is possible?
Yes, once your app is built using PhoneGap Build, you would just upload the .ipa file to iTunes Connect (you'll need a Mac to do this) and then patiently wait for Apple to approve your app. Remember to build using your Distribution Certificate, otherwise it'll be rejected upon upload.