Hi Gemma,
> When I set the initial extent to be the same as the web map this works but as soon as I launch the web app it moves to a more zoomed in scale? I then click on the home button and nothing happens.
I just tested your web app: ArcGIS Web Application and it seems to be working for me. When the app initially loads, I see this extent:
Then I zoomed in and panned around the map to view the content at a finer scale:
Then I hit the Home button and return to the original spatial extent when the app loads:
Is this not the behavior that you want?
Hope this helps,