Fern Lodge is one of the cabins at Burnside Park. It's on the edge of Keswick. You're in a quiet spot but you can walk into town in about fifteen minutes.
It's a pine log cabin, sleeps four. Two bedrooms, one bathroom. The bathroom was redone a few years back. It's got a 4 Star rating, which means it's comfortable and well-equipped. There's a decent sized balcony at the front. It gets the sun.
The site is at the bottom of Latrigg and Skiddaw. You get a good view of the fells from here. It's a proper base for walking.
Facilities are what you'd expect: there's a dishwasher, a washing machine, TV, WiFi. Bedding and towels are included. There's parking right outside. They've got a cot if you need one. No dogs, I'm afraid.
Keswick has the usual shops, pubs, and places to eat. There's a pub nearby. Derwentwater is a short walk away. You can get a launch from there.
For bigger days out, you're right in the Northern Fells. You can walk up Latrigg from practically the door. Helvellyn and the Borrowdale Valley are within half an hour's drive. The coast at St Bees or more gentle lakes like Buttermere aren't far either.
Useful links: Lake District National Park and National Trust Lake District.