I plan on getting the new Google Nexus 4 when it released in two weeks time.
However it is microSIM only. And I currently have a normal-sized SIM in my HTC Desire.
Do I need to cut it myself or will GiffGaff send me a new microSIM? (keeping my existing account details!).
You could cut it down yourself.Or take it to your local phone unlocking shop and they'll cut it down to size for you for a few quid.
You could report it lost/stolen but you'd lose service until you'd received and activated your new dual sim-normal size but with a pop out microsim.