Can anyone recommend a hotel in London that is under about $125 that is decent? 

We stayed on the outskirts of London in a town called Epping, it's about a 45-60 minute Underground ride into the center of London, but it was only 75 British Pounds a night. So if you don't mind the Tube ride, it's a great little hotel. It's called The Bell Hotel. 

$125 per person in London maybe! Travelodge have decent affordable rooms, they start at approx 20.00GBP outside London, but in London you WILL pay a premium where ever you stay unfortunately, plus if you are taking a car with you be prepared for HUGE car parking fee's. Also have a look at Lastminute.com 

I'd say $125 (80 quid) anywhere near central London would be difficult unless you like sharing with crawly things. Check tripadvisor where you can specify a price range and read the reviews carefully. 

look up the victory services club. it's a hotel for military members and retirees. they have reasonably priced rooms that are not bad. the are right around the corner from marble arch tube station and the bus that goes to stanstead. 

Speaking from experience:

PRICELINE!!!!

Go to Priceline and name your own price, selecting only central london zones, and 4-5 star hotels. You'll get a great price within your budget just about guaranteed.

Go to betterbidding.com for more help if you aren't comfortable with the bid process. 

Can anyone recommend a hotel in London that is under about $125 that is decent?

Are you set on staying in a hotel? There are other options but is depends on how adventurous you want to go. 

I wouldn't stay in a hostel in just any city but I think London is ok.

Also, there are families who rent out rooms for very cheap. We have stayed with "host families" and they have been AWESOME. They cooked us breakfast and gave us a private tour of the city in their car...it's pretty cool BUT I am sure people do have horror stories. 

We've stayed at the Union Jack Club before.. right now they have a 40 GBP special going on until the End of August for non-members.. (30GBP members) 

We are flying into Stansted on Ryanair. I am partial to a hotel with a private bathroom. Not too adventurous. When we get to the airport I guess I need to figure out transportation to the hotel. Is there a train that is easy to access? Buses? Cheap cabs? I don't mind taking a "tube ride". I just need a little help in planning and figuring our weekend out. 

just so you know.. Standsted isn't really IN London... you have quite a trip depending on where your hotel is in London.. there is a direct train link to the city... or you can ride the bus... a cab will cost you a fortune so skip that! 

I remember reading about the union jack hotel, in central London..,run with RAF affiliations, does military deals.....maybe that would work for you.....maybe in marble arch, I forget the details as its been a while. 

Standsted to London 

we stayed at the Vandon House for 70 pounds/night. http://www.vandonhouse.com/index.html this is half dorm/half hotel.

reviews at tripadvisor: http://www.tripadvisor.com/Hotel_Review-g186338-d209154-Reviews-Vandon_House_Hotel-London_England.html

what you get for the price is an acceptable room - it is clean but approximates a dorm room, so not plush, but you do have a private bath. Breakfast was nothing to speak of but there was a small restaurant nearly by with a proper English breakfast for nearly nothing.

we were worried about partying students but really didn't have an issue other than the amorous couple next door (and that can happen at any hotel really)

We were at Big Ben in about 5 minutes walk, and the tube connections are very close. 

I found a hotel near Russell Square for about $150 a night. There is a bus from the airport that will take us right there also. I found a good site 'London on a budget' that I googled. I have until Labor Day, so if anyone has any suggestions for places to go, great inexpensive restaurants and such, throw them my way please :) 

looks like prices might have gone up since we went now that I look at the site. still decent though. 

We love the Park Place at County Hall. If you decide you want to pay more for a hotel that hotel will NOT let you down. Its location is perfect with amazing views of the eye and Big Ben. We have stayed there everytime we have been to London. SOMETIMES, not always they have great deals on Booking.com. We have stayed there for 110 pounds per night. I know that is a bit more than what you had said you wanted to spend but if you take a look at the hotel and you can fit it into your budget I think you would be happy. I thought it was very easy to get from Stansted to London. The Waterloo station is very close to the hotel, just around the corner. You are a couple of blocks from Westminster, Big Ben, the Eye and the London Aquarium. There are also lots of little markets and restaurants right around there. 

very very cheep hotels would be in Victoria and finsbury park , Victoria would be better its close to central London there is a very long road (belgrave road )it has alot of old Victorian houses that have been made into guest houses , they are about 5 minutes walk from Victoria station where you can see the musical wicked across the street ,

Victoria station is linked to the over ground trains (they go across country) and the underground trains (your fastest / cheapest way around London)
its also the big coach station and most airports run coach's to and from Victoria bus station so it would mean not having o drag your bags around the city or pay out for cabs ,

the hotels are not all amazing quality some are better than others they are a good location though ,

you would be best looking online for some in that street there are alo , googling to see reviews and then calling them directly and arranging a room you will probably get a better deal this way , they like a bit of haggling to if you are brave, as there are sooo many hotels on that street one doesn't want to loose out to the next if you get my drift ;)

I am from London ... i miss my city lol can I come? ill be there in august for some masters exams anyway so if your there at the same time let me know ill give you a tour lol