Nothing special about Oxford at all. Pay the money, get in, do ATPLs and leave. Even the thickest of pilots can get into OAA if they have the cash. Only a very dopey recruiter will be impressed by that.
BTW, you can only use Bristol question banks if you are training at BGS. You can not go onto a website anymore. They give you software for your computer and you run it from there.
Chose whatever place is best for you, but remember that Oxford will not give a good impression (maybe even the opposite), and I bet you every penny I have in my bank account that the fact you did GS with Oxford will not mean the difference between job and no job.
It's good to want to learn, but understand that you will also have to learn wrong answers to pass the CAAs stupidly written exams. My advice is:
Learn basics --> learn answers --> do exams --> go back to books and get learning the depth.