The certificates aren't scheduled to be in schools until 9 November (though all of ours turned up before half term except AQA). The school then has to check and sort out the different sets of certificates from different exam boards into an envelope per student. It takes a while so most schools don't start issuing certificates until December.
If you took exams before Year 11 then some schools hand the certificates out when they've been checked but others keep them all so they are handed out with your main GCSE certificates. If you haven't received yours then you have a right to ask for them sooner but accept they may not have time to sort and check everything before the start of December.