Until it's activated I'll be using my '3' mobile broadband dongle, £10/month top up PAYG. Got the dongle from PC World for 30 quid. Have been using it for over a month now, originally working from home, and it has been very reliable when in a signal area, staying online for hours on end and as I'm not downloading anything significant or streaming anything the 1GB easily lasts a month of normal surfing.
My brother has recently had PlusNet set up at his place. Went on the cheapest package with a 10gb monthly limit and ended up paying 50 quid for the first month (
) as he kept exceeding the limit so they kept adding another 5gb for £5, and he couldn't upgrade to the package with a 60gb limit until after the month ended. He reckons he used all that bandwidth streaming YouTube music videos etc. Yeah, course I believe him. 
So a few options worth considering.

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