When buying a second hand conservatory be sure to check any paperwork from the existing owner for remaining guarantees on the conservatory you are about to buy. The reason for this is you should call the company and ask if the upvc conservatory parts are still covered under the guarantee if the conservatory is moved from the sellers home to yours.
Sellers are often after some quick money or are stuck because of financial difficulty if this is the case your bargaining position is strengthened how ever you should pay a fair price and not take advantage of someones misfortune.
The sellers often advertise on local websites or in local classified newspaper advertisements so look on websites like craigslist and preloved where sellers advertise items like home improvement products.
When calling ask for the exact dimensions and the roof type take a note of these dimensions and call a local conservatory company and ask for a quote for a supply only conservatory similar to the one you are looking at buying make sure you mention the correct colour as prices differ between different colours and grains.
Get at least three prices and you should be looking at paying at least 50% less than the prices you have been quoted and find out at the same time how much installation costs will be.