In England and Wales many conservatories don't need planning permission.  However, it's always good to check.  Ask your conservatory installer for advice - all the companies recommended on this website will be able to advise.  Check with the planning department if you have any doubts.

As a general rule you'll need planning permission if:

1. You build within 2m of the boundary line and the highest point at that junction is 4m or more high.
2. Your conservatory covers more than 50% of the original garden.
3. Your planning development rights have been removed.
4. Grade 2 listed buildings
5. Where a conservatory is 20m or less from a road or public footpath.
6. Permitted development means a property can only be extended by 50-70 metres.  This is accumulative, if the property has been previously extended, the conservatory added to the previous work exceeds permitted development levels