Must a have a visual check of all gas appliances, that was what I was told. I have a Combi in the loft as well and he did check to make sure it was working.
That was what happened to me, he checked all my gas appliances. Said my installation didn't meet current standards, so the gas supply would have to be disconnected. I refused to let him, so he called out the gas company.
I learnt from the gas company fitters that these meter changers are paid per visit, whether they actually install a meter or not. So they will find any excuse not to fit one, so they can get away as quick as possible. And they only have the training and tools to change meters, they can't do anything else, like disconnect an appliance that does not meet current standards. In my case, when the gas fires were installed, they only needed an openable window in the room, now the requirements stipulate a permanent ventilator.
My recommendation to anyone thinking of getting a smart meter is to make very sure that your gas installation meets current standards.
My smart meters took 3 visits from meter changers, two visits from the gas board, and one visit from the electricity board. Never again.