Renewal fees charged to tenants by agent

Letting Agents

My daughter and her partner currently rent a property via an agent. their tenancy comes up for renewal in a couple of months. the agent has written demanding £ 90 from each of them in order to renew the tenancy. No mention of renewal fees were made prior to taking on the tenancy and the agents website simply refers to renewal fees as cheaper than the average agent. 1) Is it common practice to charge per tenant when renewing a tenancy and would this level of fee compare cheaply with the average agent?. Further, the agent wants the fee paid 2 months before the end of the tenancy. Many thanks for any suggestions