I’m really sorry to hear that you are being asked to pay such high agency fees.
The question of whether or not these fees are allowable is a bit complicated at the moment as it is the run up to the Tenant Fee Act (2019) which comes into place on Saturday, 1st June.
We would always recommend that you seek independent legal advice about your specific situation. Both Shelter and the Citizen’s Advice bureau will offer free advice so I’ve added links to them at the bottom of this post.
However, to answer your question generally, it really depends on when tenants are asked to make a payment. For example, with OpenRent the only costs to tenants is £20.00 per reference. If a landlord asks tenants to cover these costs before the 1st of June then this is okay, even if the tenancy starts later. This is because the request has been made before the Act.
What a landlord couldn’t do is sign a contract with tenants and then ask the tenants to cover costs, that apply after the 1st of June.
I hope that this makes sense, and as I mentioned, we’d always recommend that you seek independent advice on your specific situation: