I am also a solo female traveller this year, I’ll be going on the Iberian Voyager tour for 21 days then spending a week in Barcelona by myself staying in a hostel.
Just from experience and although you have chosen to stay on a hotel, I strongly advise solo travellers who are scared of being too lonely on their holiday to stay in hostels. They are an excellent way of meeting new people, as you will be staying in shared accomodation and that will somewhat fore you to adapt to meet new people. Solo travllers in hostels are usually in the same boat as you, so finding friendly people in hostels is much easier than you think! I stayed in a hostel in Edinburgh last year and it was one of my greatest memories as I met great people and had great days and nights out with them:) Check out hostelworld.com for hostel reviews by travellers, thats how I choose my hostels:)
If you arn’t staying in hostels, I also suggest taking walking tours, you get to meet fellow travellers as well. They are sooo many walking tour companies in London. I highly recommend the neweurope tours/Sandimans. They are free (excellent tour guides who work on tips) which last around 3 hours. London Walks is another good company, they have heaps of specialised tours, from basic London sightseeing to dedicated Harry Potter and Beatles tours. Avoid any ‘bus’ tours for London sightseeing, London is a very walkable city and you will miss the beauty and energy if you sit in a bus all day long!
Hope this helps! ;D