Sup. I work at Greggs.
Honestly, a lot of the time getting a hot pasty is down to strategy. If you come in early morning, when there's not many people and everyone wants bacon rolls, then they're going to be cold. People aren't buying pasties so we have no reason to bake more if the current ones haven't been sold. The best time is at lunch time, everyone wants one and it's only the more unpopular pasties (bacon and cheese, vegetable, etc.) which might get cold.
We want you to be able to enjoy your food as much as you do, but our hands are tied with what we can do. We can't reheat pasties for quality and health and safety purposes (bc of course you would blame the incompetent girl behind the till if she accidentally browns it more than you'd like when putting it back in the oven). Plus there's the whole issue of pasty tax which people have put on here, as well as the fact that they aren't marketed as hot in the first place. If you want guaranteed hot food, then pay more to buy from the hot to go cabinet or a hot baguette.
I try to warn people when they're less than warm, but everyone have different preferences. Some people won't have anything less than boiling, others are happy with lukewarm fillings. A lot of people ask me what's warm, so I check all the pasties to let you know the warmest. I don't mind, but if I warn you and you still complain about it, you're going to quickly get on my nerves. I've had people swear at me because their favourite pasties aren't warm.
If you really want a guaranteed hot pasty, then ask one to be cooked fresh for you, which will take about 15 mins. If you're lucky, they might offer you a free coffee whilst you're waiting. Or, take it home and put it in the oven for a few minutes like I do. Just remember through all your complaining that at the end of the day a lot of our shops donate unsold pasties to homelessness charities. I don't think they're too fussed about their chicken sauce being congealed.
And btw, if you have a massive tantrum about it, the person serving you is definitely going to laugh about it with whoever else is on shift.