I spend much of my time around the local reserves. But an area I am discovering is a little further north - the Cambs/Lincs/Northants/Leics border area. It's quite under-estimated. Some are close enough (Old Sulehay, Bedford Purlieus) for fairly frequent visits. Some small reserves (such as Robert's Field) have a remarkable variety of interesting species. And some of the historic places (Liveden New Bield is one) are set in species-rich settings.
Nothing too remarkable, but no shortage of options.