What is the best method to get mobile wireless internet when I'm away from home without wifi? Do I need to get a dongle from a mobile phone carrier?

Hello,

I work in a number of Courts in the UK and part of my job is to send in reports of my cases via email, immediately after they have finished.

However, in the Court buildings there is no wifi and there are no wifi hotspots either. I would like to use my Macbook Air to compile these reports as they can be lengthy and it would be impractical to do it on my iPhone and my iPad is not 3G/4G enabled.

Can anyone recommend a method of getting onto the internet via my Macbook? I have looked into wireless dongles from the mobile phone providers? Is what I need? If so, are there any recommendations as to which are the best?

Thanks for the help!