Had a lovely weekend in Oxford last year, a great place for a historic walk. The obvious pub to visit is the Sam`s pub (Three Goats Head I think) but if you buy a guide book the `Morse` pubs are really good. Sorry can`t name any off the top of my head.
Also if you are into walking and want to visit the SS pub The Mill Inn at Withington, (20-25 minutes from Oxford) there are some great walks around Chedworth Make sure you take in Chedworth Roman Villa.
It is thirteen years since I lived in Chester so I am not sure what the pubs are like now but I believe The Albion (just off the City Walls) is still worth a visit. As for walking, I would recommend any of the walks off the Sandstone Trail.