Once resident in the UK for a certain time period, you can gain settlement status and full British citizenship.
Settlement means permanent residence in the UK, and it gives you the right of staying in the UK indefinitely and of being able to work and move without restriction (i.e. without the need for visas or work permits). However, you cannot leave the UK for more than two years at a time or you run the risk of losing your settlement status.
Settlement status can be obtained:
To become a British citizen you need to fulfil certain conditions:
You can also apply for naturalisation if you are over 18 and married to a British citizen, as long as you are allowed to live in the UK as a permanent resident, and you have lived in the UK legally for at least three years (with no more than a total of 270 days spent abroad, and no more than 90 days on the year leading up to the application).