I fish a few rivers in Dorset buckshee :-) One, is arguably the finest untouched chalkstream in the country where 2-3 totally wild 2lb brownies can be caught in a 1hr session. However due to the fact is it totally un-managed (and totally wild) it's only practical to fish during the winter, spring and early summer before the vegetation takes over. It has a fantastic Mayfly hatch and the phrase "Duffers Fortnight" may well have been used to describe this stream.
The other river I fish is the Stour which has a few trout but where they lack numbers they make up of it in size! I have caught fish to 3.5lb and know of 2 fish I'd estimate at around 5lb. There is also a good stock of Grayling, Dace and Chub to keep your rod bending! There are also a few Sea Trout and I was chatting with a guy a couple of months ago who said that he'd seen a couple of Salmon last winter spawning?
Both these waters are free and between 1/2 - 3/4 miles in length. PM me if you want details...
There is also free fishing on the Hampshire Avon north of Salisbury...
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Clubs that have fishing on the Stour are Wimbourn AC and Blandford AC. I believe both charge in the region of £80-120 per year for membership. As well as trout the Stour has some monster Pike and Perch, both of which I'm gonna have a go for this winter.