Any idea how this is best achieved?

You can do it in iTunes. With the iPad connected and selected, check out the Info tab. You'll find a place to turn on Contact syncing and select the program to sync with.

I think Google is the better method. Sync your Outlook contacts with Google, then sync the iPad with Google as well. That way your contacts will stay in sync without worrying about when you last connected the iPad to the computer.

The account on the iPad must be set up as an Exchange account. Setting up Google Sync with your iOS device : Mail, Calendar, & Contacts - Google Mobile Help