Anyone got GMS shield working the arduino in the UK

Hi All.

I wonder if someone can help. I want to be able to send and receive sms messages using a GSM shield. I am currently trying DFRobot SIM808 shield. But just can't get the GSM indicator to come on - so therefore not picking up any network. I have used an O2 sim as will as an ASDA sim. Just wondering if anyone in the UK have got a GSM shield working and if so what components are you using and also what sim card works for you.

Thank you.

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