I did BUNAC from dec 2004 to may 2005.
In regards to the bank acct...I actually still have mine, although there is just about a pound or so in it...:-p
Also, for the National Insurance Number, BUNAC set up the appt at their office, and you just bring in what is required, then eventually get the card, change the address, etc etc...
It does take some effort on your part to find a job, but I would totally suggest signing up with Manpower, cuz that served me well!