A standard (3G) dongle is extremely unlikely to support reliable video streaming. The bandwidth simply isn't good enough.
You'd need 4G which, at the minute, means that there's only EE as a service provider. Further, since they're still rolling out 4G coverage, you'd need to check whether 4G is available where you'll be:
https://explore.ee.co.uk/coverage-checker
If it is, look for dongles shown as having a 1 month contract period here:
http://www.broadbandgenie.co.uk/mobilebroadband/4g-mobile-broadband?showAll=1#featured
It might also be worth checking whether there's a BT Wi-fi hotspot in the area. Use the postcode checker here:
http://www.btwifi.com/
If there is, take a look at the payment options shown on that page (and check out 'Subscriptions' as well).
Chris