Hi bored
You've given no indication of how long ago you faxed your ID through. This is handled by the Swiss office of IB, so you also need to allow time for liaison between UK / Swiss / US offices.
Opening an account with any US broker takes a long time - it's not peculiar to IB. Blame 9/11 and money laundering for the additional work involved on both sides to meet the new US Federal laws which were introduced supposedly to thwart laundering.
If I recall, my initial account took about two days to set up, and then once you've got the approval, you can then fund it which will also take a few days to clear through the UK banking system (assuming you are funding in sterling via electronic transfer).
Having opened an account, you have 30 days in which to fund it, otherwise the account open status reverts, and you have to start the process all over again - this could help anyone wishing to open an account to know that they can leave themselves plenty of time for all the paperwork before needing to cough up the dosh.
I'm sure you'll find the wait well worth it, and hopefully you're putting the time to good use by playing with their simulator to familiarise yourself with the TWS platform