It depends on what time period of England you are interested in. The book Black Tudors by Miranda Kauffman has some great chapters about Black and Brown women from Renaissance England, for example. That would be different than the usual focus on figures like queens from the period, so it could provide a fresh approach for your thesis.

You could also focus on historical writers like Jane Austen, the Brontë sisters, Agathe Christie, Virginia Woolf, George Eliot, Aphra Behn, Enid Blyton, or Mary Wollstonecraft. They're all very different and have their own merits and controversies (note that all the women on this list are white, for example) so there would be a lot of material to work with there. Plenty of articles and books have been written about all of these women, in addition to the books they left behind themselves. The British suffragette movement might be another example of how you could look at white English women's activism for women's rights and how that did or did not include women from other demographic backgrounds. Victorian women activists working on things like restricting child labour might be interesting as well.

Of course there are also the queens regnant of England: Boudica, Ælfwynn of Mercia, Matilda, Mary I, Elizabeth I, Mary II, Anne, Victoria, and Elizabeth II. You will be able to find tons of works about each of these women. On the other end of the economic spectrum, there is a lot that has been written about women in working class English history, such as textile workers during the industrial revolution.

You've asked for "sources" but without a more specific ask in mind, it's hard to give recommendations. If you could specify the period and types of women you're interested in, we might be able to help more to point you towards sources.