Have you tried eBay? Or Gumtree?
You may not want to book via eBay but many 'private' cottages are let that way as it's considerably cheaper than using a holiday lettings company. I've noticed that a lot of the listings have links to the owners own websites so you can book direct if you like. The auction facility seems to be a common way of shifting last minute availability at lower prices.
Someone recently added a thread about dog friendly accommodation on Anglesey - you can see Snowdon on a clear day!!
We've just booked a 'dog' cottage in Aberdeenshire through
cottages4you. I didn't think their prices were too bad but I'm still amazed at how much it increases during kids holidays...