Sorry, am I right in understanding that you've lived in this rented place for 10 years and they're charging a fee to extend another year? Never head of that, personally.
Can you just go onto a periodic? That should have no fees?
I've let out a few properties and also rented multiple times before. As either a landlord or a tenant, I've only had to pay when a new tenant moves in or I've moved into a place. Most switch to a periodic once the intial 6 months lease is up.
Stuff like this gives good agents and landlords a bad reputation. I suspect the landlady doesn't see any of that £630 or even know you're being charged again to continue living there in addition to the rent you already pay.