As an individual MP you have two explicit powers:
- You can vote in any division of the House of Commons. You get 1 vote, the same as every other MP.
- You can ask to speak in any debate in the House, and try to persuade other MPs to vote as you do.
You can get more influence by becoming involved in the law making processes:
- You get to propose new laws. Most legislation that is proposed by individual MPs doesn't get enough support to become law, because the government controls the amount of time each piece of proposed legislation gets, and doesn't allow for substantive debate on non-government bills.
- You can try to join a committee: there are committees that work on the details of each piece of legistlation, and committees that check on the workings of each government department. These committees can have lots of influence.
- Since you are in Westminster now, you can meet up with members of the government, in their offices, or in the Westminster bars or restaurants and tell them about your ideas, to persuade them directly. You couldn't have done this before you were an MP
Finally you have one big piece of soft-power
- You are a new superstar! You have just done something that very few people ever do: you have beaten all the main parties in an election. This means that all the TV stations will be interested in you (for a while). You will have lots of opportunities to go on TV and talk about your ideas.
Is it possible for one MP to change things? Yes, but not quickly and not directly. You are, however, better placed to change things as an MP than as a member of the public.