If you want to see a show, then you should set a price limit first. Because some are like £50 (Les Mis, Phantom, Joseph etc) and some are more like £20-30 (Avenue Q, Wicked, etc). And some are much cheaper (Stomp, i think, is under £20). But generally, they are expensive to get good seats, unless you get an offer. Oyster had a 2-for-1 offer a while ago, which made it cheap. I dunno if its still on though.