As a non UK resident you may find it difficult to obtain temporary car insurance if you are looking to hire a car. The only way around this, is to bring your own car into the UK and to make sure your policy covers you to drive in another country. This insurance will usually have to last a year, so unless you intend to live in the UK for 12 months this will not be appropriate for you.
In order to drive in the UK, you will need to have an international driving license. Some driving licenses will not be valid (American driving license, for example) so it is important that you have legal proof that you can drive.
If you do find temporary car insurance for a non UK resident that suits your needs, you should expect to see a rise in premiums. This will be compared to people who have been driving in the UK for a number of years. Insurance premiums are usually higher because your experience on UK roads is limited and therefore you are at a high risk of having a road accident.
The road laws in the UK maybe a lot different to where you usually drive, so you should take time out to read up on the rules and regulations to ensure your own safety and others on the road.