Some of the older folk who are born and breed over generations that have never left Oxfordshire do have a more of an accent of sorts but the younger folk (under 60-70) just don't seem to, well spoken yes but not what I would call a regional accent.
I love Oxfordshire I have to say, would never leave now, we came because this is where dh is from, better quality of life and education for the dc etc etc.
We live in a rural location about 10 miles from Oxford it's self, very good, very nice area on the whole, I wouldn't personally go for Didcot, handy for the commute but not the best, not the worst either though!
There are some fantastic preps about, loads of them, I have friends who send their dc to The Dragon school and are happy with it, Abingdon prep is also meant to be good but from what I have heard I would avoid Copethorpe. There are also some fantastic state primary schools also, the one in our village that my dd (and in time my ds) attends if fantastic, only Oxfordshire school to achieve outstanding in all areas from Ofsted, normally in the top 100 for SATs results (although being a small school and often only having a SATs cohort of 16-20 means that each child represents a high percentage, this year for example there where more children with extra education needs that pulled scores down somewhat, still almost half achieve level 5s and in previous years 100% achieve level 4, this year one child didn't quite make it but it was a great result even though the head is not keen of SATs at all) and the pastoral care at the school is amazing, all the staff know all the children (140), their parents and their younger siblings, we feel blessed to live in catchment for this school, several people I know have taken children out of prep for the school not because they were unhappy with prep or struggling with fees, they just realised they were paying for something available free in the village!
If you where to move to Oxfordshire I would recommend west Oxfordshire and a good part of the vale of the white horse, I would avoid Oxford it's self, there are a few bad areas and the good areas are extremely expensive, the out laying villages are on the whole lovely though, train links to London are great although if you want to live near enough to a branch station to be able to walk you will pay a premium, Long Hanbrough is nice and has a station but really you can drive to Didcot parkway or one of the branch stations with ease from almost anywhere.
Sorry for the epic post, I love my adopted county lol!