Not necessarily, unless it is part of a larger project involving a house refurbishment or similar. Check with your local Installer for all the building regulations and rules regarding conservatories.
Conservatories are usually simpler than a full extension to a house, and for smaller conservatories, you may not need to apply for planning permission if the construction does not extend too far from your existing walls. Conservatories are available in a variety of different styles, and while your new conservatory will be specifically manufactured to the size and shape required, unless it is a very complex system, it will not usually need to be designed by an architect.
When speaking to your Independent Network installer, you will be able to discuss the size and design that you want and they will be able to give you an accurate quote for the work to be carried out, as well as giving you information about how your chosen design will look on your home.
If your property is subject to restrictions on building, such as listed status, or being in a protected area, you may need to consult with an architect in order to ensure that you meet any requirements that are in place.