Have a look at a 6" OS map - which may be found in the Local Studies section of the main public library. It's a lovely photograph of British countryside and the circle appears to be a small 'henge'. The parallel lines you mention are maybe Ridge and Furrow remnants - a ploughing system nobody has been able to replicate and which may have been connected with strip cultivation.
If the circle is prehistoric then there's bound to be other stuff nearby ...
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