I believe I can only recommend hotels I've been to, so that's why this list is limited. Some hotels may look expensive but the trick is: go to the website and look for offers or inspect the calendar and search for cheap nights (like Sunday nights or in 'dead' periods like the beginning of February).
APPARTMENTS & ROOMS
I can recommend Airbnb, which is an online community marketplace for people to list and book accommodations around the world. I've tried Airbnb once in London and I had a lovely experience! I've used the service before to visit NY, Lisbon, Budapest and Croatia and I've never had any problems. For London it takes some time to look for a nice place on a good location which isn't expensive. Rooms are around €60 per night for two persons, entire flats are €75 and up. Always check what's included in the price and read the reviews!
Check out 'my wishlist' on Airbnb.
As an appartment I can also recommend Urban Villa, which I describe below. They call themselve 'no ordinary hotel', so that's why I've put it with 'hotels'.
HOTELS - TRIED AND TESTED
81 Great Eastern Street
London EC2A 3HU
θ Old Street
Loveable because of the soft beds and cosy design.
My favourite hotel in London, even in the world! Do you need more information? Design hotel in trendy Shoreditch with spacious rooms -small sofa incl.- and a separate (spacious) bath room with rain shower. Very friendly staff! You get your breakfast delivered in a paper bag to your room in the morning. This might be a small disadvantage to some people: the breakfast you get is limited. But if you want a croissant or something else; there is an EAT and Prêt à Manger only 2 minutes away, The Attendant is accross the door and The Hoxton also has a lovely restaurant downstairs.
Citizen M - Bankside
20 Lavington St
London SE1 0NZ
θ London Bridge
Loveable because of the beautiful design furniture.
One of the most beautiful hotels in London according to me. Very stylish and contemporary. Beds are kingsize (2 x 2m) and you have a tablet to control the lights, tv and curtains. Rain shower in your room as well.
Great West Road
London TW8 0GP
θ South Ealing
Loveable because it's no ordinary hotel.
It's Brentford, so you're not in central London, but it's still the real London experience. Because London is more than the Big Ben, you know! The rooms are 'villas', so in fact you choose a studio or an appartment, which gives you a real at home feeling. Beautiful design and stunning view. One of my favourites.
7-19 Amhurst Road
London E8 1JW
θ Hackney Central (overground)
Loveable because of the nice black and white interior.
"We don’t think that a stylish, comfortable hotel bed should cost the earth." This is what this hotel stands for and I totally agree. Location is good (next to Hackney Central) and it's everything you need, but I would only recommend it if prices are low. Rooms are rather small (go for Kip Medium as a double room) and the entrance is a bit weird. They share the building with another hotel, so you have to ring the bell to enter. Reception is on the first floor with friendly young staff. They have all sorts of rooms: studios, single rooms, double rooms and family/friends rooms.
419-437 Hackney Road
London E2 8PP
θ Old Street + bus 55
Loveable because it's in Hackney.
Just outside the touristic centre in the alternative and the creative eastern part of London. The rooms are quite basic but they have a modern design (open since 2008).
8-18 London Bridge St
London SE1 9SG
θ London Bridge
Nice and cosy hotel in a lovely neighbourhood, close to Borough Market and The Shard. Underground station only 2 minutes away. Quite expensive though... (I stayed there before the Shard was built.)
1 Bedford Avenue
London WC1B 3GH
θ Tottenham Court Road
Don't go there.