There's so much in the South West within a couple of hours of you!
Avalon marshes in Somerset, go in Jan for big numbers of wintering ducks and the starling murmuration. Don't need a guide but there's plenty available in the area if you want one.
Otterton in Devon for the beavers, early summer. The restoration area between there and budleigh salterton good for a wander during the day. There's one individual that's known for being fairly unbothered by people and is easy to see.
Forest of dean for boar and pine Marten, but book a tour/hide or you'll just have a disappointing walk around the woods.
Purbeck, Arne and Poole harbour especially in spring for just brilliant habitats, but also Dartford warblers, sea eagles, waders, big landscapes.
Kimridge bay or lulworth for snorkeling in summer.
New Forest for nightjar in summer.
Salisbury plains for bustards (book a tour) and stone curlew. Two of the UK's weirdest birds.