I have found a gorgeous and unique venue to get married in and its a Treetop House in Alnwick Garden, Northumberland. You can also use the main gardens for a larger wedding party but for a more intimate affair the Treetop house is amazing.
High in mature lime trees outside the walls of The Garden is The Treehouse, one of the largest in the world. The Treehouse is so at home in its environment that it appears to have been there for many years, and the experience is nothing if not unusual.
Wooden walkways climb up into the treetops, and across a decked veranda with walkways and bridges leading out into the tree canopy. On the veranda, featuring tables and chairs and The Treehouse bar, is The Treehouse restaurant, a unique and surprisingly spacious structure. When inside, the roaring log fire, soft light and screens of fallen branches, create and other-worldly, magical environment. With distinctive handcrafted furniture and glowing candles, the space is warm and characterful.
The treehouse, just looks stunning, have a look at the PDF brochure:
How unique and spectacular would it be, being wed amongst the trees with a log fire warming you, a glass of champers and all your friends and family, so gorgeous.