Will still need to be capped, even if its dead, chances are its been disconnected just outside the wall. A gas safe guy could break the floor out at the bottom of the upstand and see if they can trace it back to a joint.
gas safety regs say it should be capped even though dead main and can only be cut off and removed if proven dead by national grid it may still be connected to a main but turned off outside in the ground, i would not cut if off until you have had it checked.
so I phoned national grid or cadent as there called now and they had a bloke round in 30mins (I didn't phone the emergency number lol) and the bloke just looked at it and said cut it off!!! took my new meter details and give me a job number. so I guess i'll cut it off then thanks for your advice guys.