Tenant denying access

Access

I have been trying to arrange access to do the annual gas safety inspection. The last certificate ran out in September this year. My tenant says she has various health problems and hospital appointments. I asked her to provide various days and times I could arrange the inspection she literally gave me a date of a Saturday morning at 8 am being the only day she would be available. I told her this was unreasonable and arranged a check giving her 24 hours notice and she said it wasn’t possible. I then arranged another check giving a further 24 hours notice and she refused and stipulated 2 further available dates and times a week later as long as I told her the exact arrangement by that evening. Only access to her kitchen is required and she refuses not to be there.
I accused her of being deliberately obstructive and trying to prevent me from carrying out my duties as a landlord. I cannot arrange this on her terms because every gas fitter is too busy to be messed around like this and even British Gas only do am and pm appointments.
This is a tenancy whereby I am unable to issue a section 21 notice as it’s very old. Advice would be very much appreciated.