Is my gas heating and hot water being stolen?

hellow follow gas meter outlet to your flat or turn off any gas work in your house record initial reading on gas metre in the morning . during night check the reading again if different. dont forget you might have gas leak as well thanks FIT&SERVE

If your pipes run under the floor boards and its timber floors... Yes. But surely you'd know if you had a combi boiler and it was coming on all the time when you weren't using the hot water tap and your heating was not turned on? If they had tapped into it, your boiler would have lost significant pressure whilst they had done this? What makes you think they have done this?