Dealing with landlords and contracts
Like offices, landlords come in all shapes and sizes. Often this can be determined by the size of the property you are looking at. A large office complex is likely to be run by a management agency and you may be somewhere down the chain from the actual owner. If you are looking at a small office for two it is likely that you will be dealing with the landlord direct. Who ever your landlord is, make sure you have a firm contract in place and try to foster a healthy relationship.
It is important that you are familiar with your rights and you should have a look at the Landlord and Tenant Act 1954. The purpose of this act was to protect tenants from discovering that at the end of their lease the landlord could either ask them to leave or could charge extortionate rent. There was no compensation for the loss of goodwill if he failed to obtain a new lease and had no automatic right of renewal. This act provided business tenants with the right to a new lease at the end of the term on similar conditions (apart from rent). The Landlord is only allowed to increase rent up to market value.
Different landlords will have different look to lease for different periods and some are more flexible than others. If the lease is for a longer duration (say 10 years') there is the chance to build break rights into any contract.
Another question is who is responsible for repairing defects in the building. A tenant should think about carrying out a survey before committing to a full repairing lease otherwise they could be in for a shock. This will give evidence of the state of the building and you can use this to negotiate with your landlord. Make sure you agree with your landlord the state and condition of the building before vacating the property to avoid being issued a "schedule of dilapidation" (under which you would have to pay expenses for repairs and lost rental time!)
Other factors for consideration are Fire Safety Regulations, and Health and Safety requirements (the commercial lease will usually outline that the tenant observes these factors).
This is a wide and complex subject so seek legal help if you are in doubt.