Hi, and welcome to the forum.

You say you "may Have an opportunity" - which sounds like you have some possibility of a job offer. Generally, it's far easier to find the job first and then have the employer handle the matter of getting the visa.

But the chances of getting a job and how much the salary will (or should) be really depend on your experience, how well you interview and the precise job you are going for. Also exactly where in the UK you will be employed.
Cheers,
Bev