Hi Oli,
Sorry for the delay in getting back to you.
You would need to use an app to allow that, possibly something like
appcrawlr.com/android/mobilock-kiosk-lockdown
but I haven't tested this or any other lockdown apps so couldn't recommend this or any other...
If it can lock down the apps and a browser to a particular address then it 'should' work though...
Sorry I cannot be more help. We would be interested in hearing back though if you manage to get it to work well as i'm sure other would be very interested in this...
John