Finlay - there are people on our current area course who did not, for differing reasons, attend anywere prior to their stage 3. They got through fine, but it comes down to the person.
If asked "Have you visited anywhere", and you answer "couldnt be bothered" - stage 3 may not go well! If you have a reason why you didn't / couldn't, just be honest.
That said, having seen all the disciplines before I started, it made the choice whether to do area or aerodrome easier, so if you can, it really is worth it.
Good luck.