I agree with the questioner who said we have enough careerists as MPs already. The party I belong to had 3 Militant Labour MPs in the 80s, who only took the average wage of a skilled worker in their constituency. We need politicians with principles, who will stand up for ordinary people, not the current lot of overpaid, backstabbing incompetents who are on both sides of Parliament at the moment.
To become one - there are two ways. Join a main political party and become adept at toadying, lying and sucking up to people. You will be rewarded about £60,000 a year plus a ridiculous amount of expenses, which you can fiddle by employing members of your family. it also helps if you have gone to public school and have got a degree from a good university.
Or stand as an independent candidate or join a small, principled party. Then campaign on an issue which local people care about, and stick at it. It will take a long time to win over people and convince them that you have a chance of winning - especially with the grossly unfair first past the post system, which gives little chance to small parties.