We need to fit a service hatch between a plant room and a service corridor. It should be 1hour fire rated. Can we simply use a small door of 1mtrs square with a closer and latch or does this break the rules. Can you supply such a door and frame please and if so how much. Thanks

If you can get a 1hr fire door of those dimensions then you could use it, also it would not require a self closer, providing its kept locked when not in use and the appropriate sign displayed. You could try a bespoke fire door manufacturer or have you considered a fire shutter similar to the ones used on serving hatches.

Mann McGowan sell fire resisting laminate called Palusol® SW which is a ready made laminate board that can be used to manufacture flat and raised + fielded-fire resisting panelled doors. Check it out it may solve your problem.