Much economic growth is concentrated in the South-East, so you should bear in mind that regional unemployment is higher in northern England, Scotland, Northern Ireland and Wales. There are also certain sectors where job opportunities are poor, such as manufacturing and heavy industry. If you are not eligible to work in the UK, you need to be aware it may be more difficult to obtain a permit than a job.
If you are looking for professional or well remunerated employment, high English language ability will be a requirement for the majority of positions. Depending on the type of job, qualifications may also be important (although not as important as in some countries – e.g. to work in a general business role, your experience will be taken into account ahead of whether or not you have studied business).
If you are studying or learning English and looking for a job to help with or cover living expenses, you will probably not have too much difficulty. The labour market in the UK is flexible and it is relatively easy to find part-time or casual jobs (even if your English is very poor!), however, do not expect to be paid much or get benefits.