The legal position with regard to the Landlord & Tenant Act 1954.

We acknowledged that with a renewable lease is that the tenant has the right to renew the lease at the end of the contractual term. However, there are certain exceptions to this rule and these can be summarised as follows: -

1. Where the Tenant is responsible for repair and maintenance the Tenant ought not to be granted a new tenancy in view of the state of repair resulting from his failure to comply with his obligations.
    
2. Due to the persistent delay in paying rent by the Tenant.
    
3. Due to the breach of any other substantial terms of the Lease by the Tenant.
    
4. That the Landlord has offered and is willing to provide or secure the provision of alternative accommodation for the Tenant upon terms which are reasonable having regard to the terms of the current tenancy and to all other relevant circumstances.
    
5. Where the current tenancy is a sub-letting of part only of the Premises and the Landlord wishes to let the Property as a whole.
    
6. That on termination of the current tenancy the Landlord intends to demolish or reconstruct the Premises.
    
7. That the Landlord intends to occupy the Premises for his own purposes either for a business or as his residence.

So a secure, renewable lease is not 100% guaranteed you must stay within the terms of the agreement else the landlord can give you notice to vacate.