Hmmm. You do know you're going to be ok the minute it's all over yeah?
Infact, you'll feel fine the moment they are doing it, they do not care about your house - they've seen it all.
They do not want to talk to you - they don't care if your busy working, they don't care if your sitting down eating a nandos at 13.05 when they show up.
It's literally a job to them and to you, it's your safety.
They will need to access to your boiler, gas meter, kitchen since you have a gas hob, and your smoke alarms.
Occasionally they put their head into the loft if it's needed.
It won't take long, 10 minutes is a stupid ideal though. I'd say more 30 minutes.
Breathe, open the door, hey how are you, boilers in there and kitchens that way.
Put some music or tele on, play on your phone, be available but you don't have to stand there and chat or anything.
30 minutes of your entire year. You so got this