Where to stay in london for two days in late April?

Premier Inns are located throughout London, the ones at Waterloo and County Hall are close to Westminster and the River and well recommended on this Forum.

You might want to consider the Premier Inn Victoria, which is very close to Victoria Station and quite centrally located. Premier Inns, which are a UK based chain of hotels, have very reasonable prices and are consistently clean and comfortable. In fact their beds are really comfortable, I found. They do have breakfast available, but it is not included in the price. You can decide whether you want a continental breakfast or a fully cooked breakfast at an additional cost each morning.

I've stayed at a number of Premier Inns in both England and Scotland and have always had a good stay there. Keep in mind that the earlier you book, the lower the price. If you arrive early they will store your luggage for you in a locked room, and sometimes you can even check-in early for a small fee (that varies depending on if they have something available).

For what it's worth I stayed in that neighborhood last year when I was there (different hotel) and thought the location was really great. I was able to get to almost any place in London quite easily. And the location is very safe. But that's true of just about every neighborhood in the city center.

Premier Inn also offers a very basic budget option called Hub with several locations around London. You don't define "we," so I assume you are a couple. I haven't stayed at these Hub places because I was traveling with someone I didn't want to share a bed with. They are literally a bed and a bathroom but centrally located and relatively low-cost. Enjoy your short visit to London!