ask your employer to check these 2 links here:
http://www.workingintheuk.gov.uk/workin ... legal.html
http://www.workingintheuk.gov.uk/ind/en ... tamps.html
They give information to employers and as well show the stamps. So yur employer will be able to see your stamp and see in the page that people holding these stamps are able to work.
You can also ask your employer on this number: 0845 010 6677***.
This line is dedicated to answer employer questions only.
So your prospective employer will be able to ask if people with Family Permit are able to work. So he can be confident and give you the job!
*** I just found out this number today! Last Saturday my EU partner sent a letter to the Home Office to update the details and passport (his old one expired) and in 1 week, really!! Only 1 week!!! home office sent a "certificate of application" letter, and in this letter it says that EU or the non-EU partner can work straight away - even without receiving the visas, etc... And in this letter it´s giving this number to employers to confirm the status of the person.