Is this a comment about holidaymakers trying to get back to the UK to beat the new quarantine restrictions?
There seems to be slight mismatch between the two parts of the sentence:
"If they've given us 48 hours" suggests that you think it's possible that they've done this, whereas "we'd all be back" suggests that you're talking in hypothetical terms.
Let's presume that the "we'd all be back" is hypothetical. In reality, they haven't actually given you 48 hours (perhaps they've only given you 24 hours) and - because the time was too short - you haven't managed to get back home before the deadline. You're complaining about not being given enough time and hypothesising about how it would have been better if they had given you 48 hours to get home.
In this case, the correct sentence would be a mixed conditional. This would be a third conditional 'if clause', imagining a hypothetical situation in the past, combined with a second conditional 'then clause', imagining a hypothetical result in the present:
"If they’d given us 48 hrs, we’d all be back."
Does that help?