Small Fireplace Renovation

I have just bought my first property, it is a ground floor flat. When I bought the property the fireplace was covered with a board. I have now taken off the board and there is a half attempted hole behind it. I would ideally like to open up the hole and create a nice open space to perhaps tile. The space will just be for show, we do not want to put in a working fireplace.

As you can see from the pictures, there is a ton of soot inside and the brick work will need work. There are bricks in the front corners of the fireplace, I am assuming they are there for support so I am not sure how we would open this up and make it square.

As a first time buyer I do not know which type of tradesmen would be suitable for this job, the potential cost and whether the job is feasible? Any help would be appreciated.