'But beforehand' is correct and usable in written English.
It is generally used to introduce an idea that comes before another. For example, "We wanted to take a break, but beforehand we had to finish the project."
But beforehand the guards had to line up for a different sort of inspection: passing through a metal detector; being frisked; and placing their rifles through an X-ray machine to make sure they were unloaded.
But beforehand, the pertinence of the protein ligand database is investigated to assess its representativeness.
[Laughs] As a kid, I felt happy onstage, but beforehand I would think, What am I doing here?
Which makes up day three of the Anniversary Games but beforehand the Paralympians will be competing at the World Championships in Lyon.
They performed at the Town Hall that night, but beforehand, looking to kill an afternoon, they played a problem-solving game on the twelfth floor of a building on Thirty-first Street.
Updated at 3.43pm BST 2.24pm BST The Bun Shop We're about to go and pick up the car, but beforehand, we had time for one quick below-the-line tip that came in late last night.
THE OLDIE BUT GOODIE Beforehand, you might be concerned about this sexagenarian's health.
Pyongyang should be ready to take steps not only at the very beginning of talks but also beforehand.
No one likes to talk about the looming death of a loved one, but asking beforehand avoids countless problems later.
When it was made, in 1968, Ashton was the director of the Royal Ballet, but shortly beforehand he had been informed that in 1970 he would be replaced.
The European Union sent a small delegation to observe the voting, but stressed beforehand that the presence of the group should not be interpreted as blessing the results.
