Buying a property with an existing tenant

Other

Hi there, I'm buying a property with an existing shorthold tenancy agreement in place. From looking around I think the following is the case but I wanted to check with someone to be sure;

When I complete the purchase I will be party to and bound by the existing agreement.
I just need to have signed up to the deposit scheme and issue the existing tenant with a section 48 notice, my contact details, payment details, details and leaflet of the deposit scheme and that I am now the landlord and they should cease payments to the old landlord?
The existing landlord can then release their deposit to me.

The existing landlord is a management firm and the owner of the property has no direct contact with the tenants, the firm are telling me that they need to issue either a section 51 or section 48 (they can't make up their minds) and that they can't give me access to the tenancy agreement files until after completion AND that they want to charge me £25+VAT per document (the tenancy agreement references an inventory and possibly a schedule of condition so they are talking about £75+VAT). The management firm and estate agent are one and the same. I have no agreement with the firm so I don't see how they can expect me to buy the property without seeing the agreement or charge me for it.

thanks

Andy