To search for a job in the UK you need to be either a UK citizen, or someone who holds a licence to work in the country.It pays to be prepared before you start your job search, regardless of where you are from.
United Kingdom Citizens
UK Citiens will already have a fairly good understanding of the UK jobs market.
One way of successfully finding a good job is by having someone recommend you.The UK places as much importance on a good quality reference as US employers, so make sure you have someone to vouch for you. If you are thinking about getting into police careers, you will almost certainly need a reference from an old employer or trusted member of the local community.Try and make contact with your desired UK employer and get a good understanding of the types of people they recruit.
After you have good references and your CV, you can start applying for jobs while you are job hunting in UK. You are bound to find one sooner or later!
Advice For Non UK Citizens
For those non UK citizens looking for a job in the UK there are many things you should understand first.If you are being re-located to the coutry for a certain reason, such as the armed forces, talk to other people who are going through the same as you.
It is possible that they will know of job vacancies which would suit you.It may be worth looking at companies who are located in your home country, to see if they have a presence in the UK.You can ask that employer if they have any vacancies in their UK offices.