Once you have signed the tenancy agreement you will technically be bound by the agreement until the end of the tenancy.
If you (as the landlord) are not happy with the terms of the tenancy agreement then you may seek to agree amendments with the tenant, however, there is no obligation on the tenant to accept these changes.
If, for whatever reason, you believe that the tenancy cannot go ahead then you should seek to negotiate a surrender with the tenant before the tenancy or renewal tenancy begins. Again, there is no obligation on the tenant to accept a surrender. If you are unable to negotiate a surrender, and for some reason the tenant is not able to move into the property, then they may seek to make a claim for damages in the small claims court.
You can read about cancelling the process and surrendering the tenancy during Rent Now here.
Information on this site is by way of general guidance only and may not apply in your particular circumstances. You should not act or refrain from acting upon information on this site without seeking independent legal advice.