If you are relying on public transport, trains, although they can be expensive the return tickets used to be valid for any time within a month and they allow you on the return journey to get off and on numerous times for days at a time. Combine this with the local bus service which go to most small towns and some of the villages - although getting the exact information can be a pain most local tourist offices especially in the county towns which are probably accessable on the internet. You could also probably get a tourist ticket for a fixed duration - you might find this helpful, the English tourist board would be the people to ask.

I don't know if you've been to the UK before just remember it is more densly populated than the US and so you might find concentrating on one or two areas might be more useful - it also means distances between places are shorter. Good Luck