I've got the 4g Huawei dongle too and a Virgin data sim. I got a crazy deal with Virgin, it was a special deal 12 month contract, 100gb a month, 30gb roll over each month for £20 a month all in. I think they only offer 40gb at the moment, but it was far cheaper than using other top up solutions.
The dongle works perfectly, I've had no issues in the UK at any locations so far, there's always been enough signal to keep the kids quiet and allow me to browse on my phone.
I leave the dongle plugged in 24/7 so I've always got a data connection in the bus, great for streaming Apple Music etc. If my wife is taking the kids on a trip she takes the dongle with her in her car so the kids can sit on their iPads.
They are brilliant, cannot recommend them enough.