Website: http://www.penrithbuildingsociety.co.uk/
Phone: 01768 863675
The Penrith mortgage products have won awards for value three years running, largely because the company is mutual, small, and cost-conscious. So much so, you'll need to ring up to find out any more!
The Penrith has consistently won "What Mortgage" awards for value across ten years; and whilst there's always more than one way to interpret value, the company has all the usual trappings of good service: it's a mutual society (no shareholders to pay for), and it's local (indeed you can only get a Penrith mortgage in England and Wales, and it's not long ago they wouldn't lend outside Cumbria), they don't advertise, and they don't have branches.
That said, there are no product details on their website; except for the information that all Penrith mortgages are flexible (over- or underpay if you wish); so you will have to call up for a quote based on your circumstances. In fact, don't bother with the site at all- just call up and speak to the real Penrith mortgage people, and see if they can match any other rate you've been quoted.