Agents taking deposits from two groups of students at once

[Rentalannoyance]

I wondered if anyone with knowledge of the rental market/tenant's rights might be able to advise.
My DD is at Uni and is living in a house share with several other students. There will be some changes to the group of students that she is living with next year, for various reasons. After some discussion within the new group, which did take a little while as no one wanted to take on a room which is a lot smaller than the others, they decided that they would stay in DD's current rental house with the new group (some new, some currently living there). During the few days that my DD's group were making a decision, the agents did show a couple of other groups, one of which was apparently interested. The agents gave my DD's group a date by which to make a decision about staying or going and my DD emailed them with their decision to stay in the property within this period and gave them details of all the new tenants, which they accepted. A couple of days later, the agent emailed my DD to request 3 outstanding deposits from her friends (out of a total of 6). She chased them and two paid immediately but one was taking an exam and couldn't send the money straight away. Three hours later, the agent sent DD an email to say that they had secured all deposits from the other group that had expressed an interest and that they would therefore be given the tenancy next year. DD and her friends are obviously upset and feel that the agent has been unfair and played one group against another.
A quick google seems to suggest that they should not be asking for holding deposits from two groups at the same time. I'm not sure there is an legal recourse here but can anyone offer any advice?

From what I know, it’s not allowed and they can (and should) report the landlord. Landlords can be fined for doing this.

It’s not going to make a difference to who gets the house though. The second group haven’t done anything wrong and may now have a signed tenancy that isn’t going to get undone.

I would have thought the deposit was part of confirming they were staying there, rather than an optional extra.
It seems like they were chased on the deposit and paid late.

Yes but a landlord should return the first group’s deposit/part deposit before they’re allowed to accept deposits from another group

Thank you!
That's what I thought on both counts from a quick google.
I agree that the second group haven't done anything wrong, although they may have been told to hurry up if they wanted to get the house, which my DD's group were not told.

They could have, it can take days for a payment to process from a business. It’s not clear that they didn’t.

Sure but they chased once and then 3 hours later emailed again to say that the place had gone. They could have given them a cut off of 5pm or something and only then returned their deposits and started taking deposits from the other group. They shouldn't have been taking deposits from both groups at the same time.