For those that only want low data from a good network, this seems ideal, it's a 30 day sim so cancel at any time.
Can I keep my number? Yes, just enter your details under the 'Switching Network?' section when checking out. Alternatively, you can move your old phone number across later, once your new SIM card arrives. Which network does Talkmobile use? Talkmobile runs on the Vodafone network so you'll get 99.9% population coverage.