For the one where you bill direct, did you ever register as self employed with HMRC?
How long have you been doing that job? If you worked it for any part of a previous tax year (before April 2010) the filing deadline for self assessment is on Monday 31st January. I need to file a self assessment return for the last tax year even though I have been advised that there is nothing payable. I was registered as self employed for that tax year as I was receiving income where tax was not paid at source via PAYE.
You can now only file online and, for that, you need an account set up on HMRC and for them to send you a code to access the site which they do by post and can take up to 10 working days.
HMRC are open Saturday mornings so it is possible to speak to someone today or Monday if this is the case as, if there is anything you should be declaring for the last tax year and you don't file in time there is a fine of £100 and interest accrues on any tax payable. I believe that all tax owed for the previous tax year also needs to be paid by 31st January.
HMRC have a very good site with lots of information and I have found them incredibly helpful on the phone. They have Enquiry Centres (details on the site) you can go into though you may have to make an appointment to see someone, especially at the moment with the filing deadline for self assessment being so close.
I don't want to panic you but, if you do need to file anything to HMRC for the tax year April 2009 - 2010 then you need to speak to them urgently. I'm not that knowledgable on all this so hopefully someone who is will confirm (though best to speak to HMRC rather than waiting for a reply here).
Hope you get it sorted.