I'm been bidding on Priceline for a few weeks and nothing is coming up, the dates I'm coming in mid July seem to be extremely busy. However, many of the hotels that appear on Priceline seem to still have availability and the area that is coming up cheapest at retail prices is Finsbury/Islington. The two listed as 4* on Biddingfortravel are (of course I'm not guaranteed either of them but I'm guessing there aren't any other 4* properties in that area):
Hilton London Islington (near Angel)
Crowne Plaza London Shoreditch (near Liverpool Street or Old Street)
Would either of these locations be unsafe for me and my 17 year old niece? I'm guessing the latest we'd be out is post theater so 10:30 or 11pm. I've been through Liverpool Street during the day and the area doesn't seem bad. I don't think I've ever been to the Angel station.