There’s always some variability in what landlords and agents will or won’t do because there’s always some possibility of unknown factors, that said:
The dream of a landlord is tenancy without voids and the best way to ensure that is to have one tenant for as long as possible. That means, usually, a landlord will allow a tenancy to continue indefinitely because any void (period where the property is untenanted) costs the landlord money and ultimately landlords are running a business so voids = bad.
You do not have to renew a tenancy on a fixed term: at the end of a fixed term the tenancy automatically reverts to a rolling tenancy (month to month). A landlord can offer to renew to create a new fixed term but you don’t have an obligation to agree to a fixed term, it’s open to negotiation: sometimes a landlord may only be willing to have tenants in fixed terms but it’s very uncommon for a landlord to seek reposession if a tenant decides they’d rather be on a rolling tenancy at the end of a fixed term. Historically agents had misaligned incentives when it comes to fixed term vs. rolling because they could charge fees to renew but given those fees are now illegal they’re much less likely to try and push for fixed term.
Some tenants like to be in a fixed term because of the security (you would know for certain that you can’t be served notice until the end of the fixed term) and others prefer month to month because of the flexibility: you can move out at any time (as long as you provide one month (period) notice).
So in summary: the power is mostly in your hands. If you want to renew then you will almost certainly have the option, you can contact the agency to confirm that you’d like to renew if you’re happy there or you can just wait and see what happens. The landlord will almost certainly be very happy for you to renew. That said, at the end of a fixed term you do not have to move out, the landlord still has to serve notice, so if on the 12 month anniversary of your tenancy you haven’t heard anything then that means you’re now in a rolling tenancy and your landlord is now required to give at least 2 months notice to end the tenancy.
 Technically, at the 10 month anniversary because in a fixed term they must still give 2 months notice, so if they served notice during your 11th month then you’d have to leave at the end of your 13th month. Notice served during 1st… 8th, 9th, 10th month: leave at end of 12th month. Noticed served during 11th, 12th, 13th, 14th… 99th: leave at end of (month + 2), e.g: 11th = 13th, 12th = 14th, 13th = 15th… 99th = 101st.