Is the fee to register my tenant with the freeholder legal?

Hello, I have received an invoice of £75 to register the name of my tenant with the freeholder. Part of the process requires that I submit the AST to the freeholder.
I have queried this payment on three levels:-

1) The name of my tenant if personal information as defined in GDPR. The freeholder has not established any legal basis for requesting and then processing this personal information (except that it is a requirement of the lease).
RESPONSE – refer me to the lease where they require the information.

2) The AST can be deemed “commercially confidential”. What is their legal basis to require this document? It is not stated in the lease.
RESPONSE – refer me to the lease where it talks about assigning payment of the annual fee to the landlord. But that is my cost not the tenants.

3) The fee of £75 is excessive. The lease (drafted in 2012) states that a fee of £30+vat is reasonable. If this is inflation adjusted then the fee today should be no greater than £44.64 (inc vat)
RESPONSE – The freeholder deems the £75 to be reasonable and this has been agreed at tribunal in “Freehold Managers (Nominees) Ltd. V. ” (it does truncate to case came).

This looks like a legal structure to create an admin process that the freeholder can then profit from? I cannot see any legitimate purpose (within GDPR or DPA) for the freeholder of a block of flats to have my tenant’s name. If there is no legitimate reason to have the tenant’s name, the process to register this name is surely voided.

Any views?

Are these charges legal?

I know it is small – but it adds up from the industry.

Thank you,

Geoff