Minimum survivable budget for a single guy

I plan on moving to the UK on the Tier 5 YMS visa, which means that I won't have a job until I get there.  What is the minimum comfortable and livable allowance per month that I should set living in London?  I've been in London before 5 years ago and I realize how expensive it is, but that was from a tourist's point of view.  Hopefully, it's different when you live there.  Anyway, are the following figures per month doable?

Accommodation (hostels for the first month until I can get a job): £300-400
Food/Groceries: £150-200
Travelcard/Oyster card (zones 1-2): £100
mobile phone: £20
Entertainment (I am willing to severely limit this until I can find a job): £30

Total costs for the first month: £600-750

Is this too little or too much?  I won't drive so no petrol/congestion charges and since I will be staying at a hostel, I wouldn't need a TV license.  Any other expenses that I'm not aware of?

I'd say a really basic budget in London, student level without entertainment and just taking the bus around (cheaper than the tube) is about 700 to 800 a month, so you should be okay. However, you'll need a little more money to move into a place, won't you? Houseshares sometimes ask for a month's deposit.  Also, will the hostel have unlimited internet and a printer for finding jobs and dropping off cv's? You also haven't included top-up charges on the phone. You can get a phone for that amount but you'll probably spend another 20 a month on pay as you go. Get sandwiches at the end of the workday from Tesco and Sainsburys at the front of the store. Good luck!

Thanks Molly.  Considering one of the requirements for getting the visa was for the applicant to have at least £1600, I will have a lot more than that when arriving to the UK.  I just don't want to blow a lot of my savings while I look for a job.

Yeah, I won't be looking for a house share until I find a job since I may end up finding one outside London.  So I'll probably stay at a hostel for a while.  Some hostels have free wifi but I'll be going with Bite Consulting to help me find a job and from what I understand, I can use their facilities while I look for one.

By the way, I'd like to bring my cellphone with me and just change the sim card so I don't really have to buy a new one.  How many minutes does £20 get you?  Is it also better to have a travelcard than an oyster card?

If I aim £700 a month, will that work?