The two basic things that you normally want to achieve when you get to Oxford is to learn English and to find a job. Both are connected. The better your English is, the more probable it is that you are the suitable candidate for the role.
First of all, you have to write your CV properly. Each country has its own way to write it, therefore, there is some likelihood of you having to change something.
With the purpose of avoiding discrimination, in the UK it is considered by law that picture, date of birth, race, sex and nationality should be omitted in the CV.  Further, it’s very important to provide at least 3 references.
Strengths…
… and skills
Secondly, a covering letter is always important in order to introduce yourself and grab the employer’s attention showing a resume of your skills and strengths. Add some reasons for why you want to get the job and how you can contribute to the company.
From my point of view, it is better to have a different CV for each application. But this is up to you!
If you are looking for a job on the Internet, I would recommend you two useful websites: Gumtree and Daily Info. The different roles are updated every minute.
On the contrary, if you prefer the traditional way to look for a job, take your time to visit the recruitment agencies in Oxford. Manpower, Blue Arrow, Champion and Reed are just some examples.
It is said that handing out your CV in person in shops, cafes and restaurants is very effective.This is  probably because your potential boss get to know you at the moment and can check your level of English and manners easily.
Finally, don’t forget that to work in England you need to have your National Insurance Number. You can get it just arranging an appointment in the Job Center, which is another place that you should visit if you need some help or advice to find a job.
Do your best in the interviews and good luck!!