What to do if tennant fails to book a gas safety inspection?

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The gas company sent myself(landlord) and the tennant a letter stating that the annual gas service was due. I sent a text to the tennant reminding him to do this, (his reply history to letters , lease renewals etc has been very slow), he stated that he would do it according to his agenda. The gas company sent a 2nd letter stating that failure to inspect could lead to a £20,000 fine! The tennant has now complied and made an appointment.
But what if he hadn't? What should I do? I have offered to stand in for him whilst he is at work, as I have done for other tennants.

1. Could I switch off the gas from a safety point of view and inform the tennant?
2. Could I make an inspection appointment and access the property?
3. Do I just inform the gas company of non compliance?

Others must have faced this problem.
Also, would it be possible to add to an AST. a paragraph informing the tennant that all communications must be replied to within 2 weeks? (tennant has taken many weeks and promptings to reply, paperwork is not his forte). Otherwise a good tennant.
Thanks for your assitance in this matter.