We had our wedding at Combe House in Devon. Glorious bedrooms, down to earth staff and amazing food. Undoubtedly the most romantic place I've ever stayed!
If you're looking for something a bit cheaper I've stayed in this B&B Larkbeare Farmhouse in Devon a few times and it is gorgeous - the website doesn't do it justice. Run by a lovely couple who were very accommodating - bought us cake and sherry in their lounge and even drove us to the pub for dinner! Very pretty location and lovely attention to detail - posh linens, etc.