I would suggest you go to your local SW office to morrow morning and sign on for jobseekers benefit. Bring P45, passport,and PPS. No. If you haven't yet got P45 sign on anyhow (you have 21 days to produce it)
Hopefully some of your interviews will be successful and you can sign off on the last day before returning to work.
Your benefit will take a couple of weeks to process and if you are stuck in the meantime go to the CWO (Community Welfare Officer) for Supplementary Welfare and rent supplement