Automatically install new apps checkbox
In the "Apps" menu of your iDevice you will see the checkbox shown above at the bottom of the list of apps. Check it and hey presto all apps will sync....along with everything else not on the iDevice. This is fine if you are running one device, but if like me there are family members using the same iTunes account and each have different apps this isn't going to work.
Summary: fine if you want all your apps on all your devices
Command key
If you scroll down the list of apps in the "Apps" menu of you iDevice and find one that needs updating, click on the "Update" button whilst holding down the Command key. Magically, all of the icons will then turn to "Will Update"!
Now, there is a catch. If you have a lot of apps that need updating and not a lot of room on your device, you may well get an error message.
If you do, find the triangle icon with an exclamation mark and click on it:
You will get a message like this:
Panic ye not! It's just there isn't enough free space to get all the apps on in one go. Just find another "Update" button, click on it again (whilst holding the Command key) and repeat the process as before. The more free space you have, the less iterations it will take. So get rid of those old apps crowding your iDevice!
Some really large apps may be left and simply won't update in a batch. You'll have to do those one at a time or free up more space.
If you can't free any more space, then try updating via the App Store app on the iDevice itself. If that doesn't work, you will have to free up more space or just keep the old version of the app.
It works - it's a bit manual - but it does work...
Conclusions
A bit of 'trial and error' has yielded two ways to get apps from your computer onto your iDevice. of course, I might have just missed a setting somewhere - so if I have - please leave a comment!