Oxford logistics with car

It should be easy enough to navigate to a parking lot closer to Oxford train station, such as the APCOA lot that is cheap on Sundays but expensive on other days or the UPark that looks like 8 pounds every day. They're on a main road and train stations are always well signed, either in words or with the birds-foot-looking logo of National Rail. I would not try to visit both Oxford and Blenheim in one day, especially while jet-lagged.

we will be jet lagged so......

So probably hopping into a car on the wrong side of the road and on to Europe's busiest motorway is not a great idea?

I'm not sure you can properly "do" Oxford in a week let alone half a day - or maybe a quarter of a day as it isn't clear by what time you would be able to arrive in the city.

You are I believe heading to Stow - I would forget trying to swing in Oxford and Blenheim together and just to the latter if you can manage it.

I definitely do not recommend seeing Oxford & Blenheim in the same day. I recommend googling to find out the "park and ride" sites in Oxford. I have driven in England many times and even if jet lag were not an issue, I would opt for "park and ride" to avoid the hassle of parking in Oxford.

Don't try to park in central Oxford. Street parking is as rare as hens' teeth and £2 for a half hour if you find it, even on a Sunday. Use the Park & Ride but many P&R lots close on Sundays - check first. Blenheim is ok if you can stay awake, and parking is easy and the place is spectacular.

If you go on a bus tour you may find jetlag catching you up more than if you were walking on the ground, either in Oxford or Blenheim, and you will have to judge how you feel after landing when contemplating hiring a car for a cross country drive after a long flight.

I'd pick one or the other - or go straight to Stow-on-the-Wold.

But since you are only 3 days out I'm sure plans are set in stone.

Coffee shops? Do you mean Starbucks or do you want home grown?

In our experience, it's not the motorways that are bad while jet-lagged and moderately disoriented. They're one direction and you pick a slower lane, don't try to pass, and only change lanes as needed at junction splits.

It's the traffic circles at on and off ramps and any city driving that will get you at that point

Oxford actually makes it easy for visitors and commuters to park...Redbridge, the one you refer to, is the one we have used...it's on Abingdon Road coming in from the south. It's perfect.
Personally, I would never try to drive in the UK after flying internationally - I don't handle jet lag well. You know yourself though and maybe it will work for you?
No on the Oxford and Blenheim Palace in one day idea. Far too much to see in both places.
If you think you can do the drive then I would suggest spending the night in Oxford. It's only about an hour drive out to Oxford from Heathrow once you get the car - depending on traffic of course. You might have enough time to see some of the city that day. You can spend the night then go to Blenheim the next day. It's only about 15 -20 mins outside of town.
I have to say that spending only part of a day in Oxford is NOT nearly enough. Two days are perfect - one VERY FULL day in a pinch.

Pear Tree could be a better choice for P&R considering the onward journey.

Driving in the centre of Oxford has many traps for the unwary; crossing the centre is convoluted where possible and there are a number of access points close in that are bus/taxi/emergency vehicle only for whole or part of the day. If you go through one of these in error at the wrong time it is a £60 fine.