The certificate can take a few weeks to come through, some people have waited longer, I think it depends on the IP and their workload.
Don't forget that the IVA will remain on your file for the full six years from acceptance.
You should request a copy of your credit record from the three credit reference agencies and make sure that no defaults have been registered since the date of approval. If there are then you need to write to them to tell them to remove them.
You can start to rebuild by keeping your bank account/mortgage/mobile phone contracts up to date. You could also try applying for the Vanquis credit card - high interest rate but as long as you pay it off in full every month then you shouldn't have a problem.
Sharing from experiences of dealing with debt
The greatness of a man is not in how much wealth he acquires, but in his integrity and his ability to affect those around him positively.
Bob Marley. http://kallis3.blogs.iva.co.uk