My son's first passport hasn't arrived - we move in 2 weeks!

Help! I am a british citizen, and am moving back to the UK from the US with my US husband, who has been aproved his UK spousal visa, and our two year old son, who I applied for his british passport about 4 weeks a go. It is about 2 weeks until we move, and his passport still isn't here. I am panicking. I attached a cover sheet exaplingin we were moving, with a copy of the tickets (one way) with the passport application. I called the Passport help line (Abran) and they 'sent an urgnt message to washington'. still no reply from washington, so I called again today and was told I had to wait to hear from washington. they wouldn't give me any contact numbers to call, or any alternative solutions.
My son does have a US passport, but I am scared to enter him on the UK on it, as we are traveling on one way tickets. any advice from anyone! is there such a thing as emergency passports, etc? does anyone know if I called the nearest british embassy if they would help me with this???

If you haven't received the Brit passport by moving day, your son can travel on his US passport. Take all copies of the correspondence relating to the application.

You can't be forced to leave the Uk, and neither can your husband. Immigration can't send your son back on his own, they'd have to let him in on some time-limited stamp or "temporary admission" which should give you time to sort the matter out. The airline on which you are travelling may be uneasy because he's only got a 1-way ticket, but they won't be liable for a fine because US citizens don't require a visa to travel to the UK. Their only concern would be having to bear the cost of flying him back to the US (which won't happen). As a precaution you should have a word with them before travelling. If necessary you could sign to indemnify them against any theoretical removal costs.