Premium seats at the theatre are expensive, but if you know where to look you can enjoy a great view for less. Seats just one or two rows behind premium often have near-identical views for a significantly cheaper price, for example. When you are booking, always check user-submitted view from seat photos on SeatPlan to get an idea of which seats are best for your budget.
Restricted view seats that are well-rated by SeatPlan's community of theatregoers are another great option for cheap London theatre tickets. Some restricted view seats are surprisingly good value for money, with pillars and other architectural features barely affecting the view.