Hi, it looks like you have received great tips on what prices are like at the moment. Also remember that prices will vary depending on the finishes. For examples you can find tiles that cost 30pounds/square meter or 200pounds/square meter. There are ways that you can achieve a beautiful result without spending too much. Its more about how much time you have in your hands to shop around for good quality deals. If you are time poor and are feeling overwhelmed, my name is Alessandra. I am the founder of Orsetto Interiors, a locally based interior designer with a background in architecture and certified project manager. I can help you design the extension and even oversee the build for you, all depending on how much involvement you want from me. I can help you source items based on your budget and you can buy them directly or coordinate everything for you and even give you access to my supplier discounts. Happy to have a chat get in touch
www.orsettointeriors.com