Many people use conservatories as a dining area, guest room or extra living area. Others may use it as a playroom or garden room. What you intend to use your conservatory for will dictate the size, layout and style.
If you are going for a conservatory with a solid roof, you can find replacement conservatory roof cost samples, but you may need to consider the extra planning permisison & building control requirements.
Thinking about fitting a larger conservatory, you may benefit from reading this article, www.orangerycost.co.uk/how-much-does-a-large-conservatory-cost, if you do this you will more than likely end up with a building that makes use of its full potential.