Also topcashback/quidco of 4-12%. This deal's been running a while but isn't well known, every week you can book on Monday or Tuesday for following Friday, Sat, Sun or Mon nights and for the week after too. Some hotels are £25 (all ibis Budgets, some styles and some Ibis) and some are £40 (e.g. Ibis London Euston). Elstree (zone 6 London) and Docklands (zone 2/3 London) are great value for around £23 after cashback. You can only book for the same week or week after. Price is per night for the room only. The room is for 2 adults and 1 child, and I think you can have a toddler/baby as well. But not two older children. You can book just 1 night, or 2 or 3.
You must be an Accor club member but it's free to join and also means you earn loyalty points towards future stays.