It doesn't have a website, so you'll have to read about the erratic opening hours and cash-only service on Daily Info http://www.dailyinfo.co.uk/reviews/venue/587/The_Isis_Farmhouse/ which apparently is wrong, and the pub's management have complained. But not tried to make their own website, and that kind of sums up this place.
Every time I go to the bar I'm wondering if I'm doing it wrong. On nearly every occasion I've been there people have fallen foul of something like wanting lunch outside the invisible serving hours, wanting a _whole_ bottle of mineral water, or taking glasses outside. Picture "Michael's Cafe" on Jack Dee's "Lead Balloon" and you're in the right area.
The cakes are really good, though we're never there in time for proper food. The beer is Cotswold Lager and some local brews like Appleford Brewery's "Power Station", so it has great intentions, and seems to appeal to the yummy mummy lunchers from Iffley & the like.
My advice: take a sunny day, walk down the towpath, buy a pint, sit outside, try not to do it wrong. Lovely beer, lovely setting, very Oxford.