My husband and I had a really good experience at the Happy Lodge. The owner was really kind to us, and even upgraded us to the Family Room from a Double Room at no extra charge. This gave us lots of room. The room itself was a bit outdated, but everything was clean and the bed was comfy, so we had no problem with it. The en-suite bathroom was also clean and had a good shower, so that was great. We never had the breakfast provided, so we can't vouch for that. There is a mini-fridge and microwave available for use though, which is nice if you want to have a meal in on your own.
The Lodge is located just north of Oxford in Kidlington, and there's really quick and easy bus access to the centre of Oxford for sightseeing. Near to the Lodge itself, there's a Sainsbury's and a few restaurants not right beside it, but within easy walking distance.
All in all, a pretty good place to stay for cheap near to Oxford.