Be calm, cforcanada ad others in the same position i.e. having received PER and needing to submit their Police check certificate at some point.
The old rules 120 day e-mail was a request that was made by the Visa Office when they were ready to process your file and that gave you 120 days maximum to submit all the docs required on the list.
This is now obsolete, as everyone sends everything at the start. The PCC only has this confusion because of the small window of time where CIO were telling applicants not to send it and their subsequent advice telling applicants to include it if they could but it was not essential. The widely held view is that this was to ensure that those whose countries are slow at providing Police certificates were not unfairly disadvantaged in the race to get in before the cap closed, which was very fair and kind, I think.
Nobody under the new rules is going to be rejected through being "timed out" on providing this document until the Visa Office has contacted them to ask for this document. They will then tell you how long you have got to submit it. Sending documents to the VO without being asked is inviting the possibility that it will be lost in the system.
Wait until they contact you to request it, then send it.
If your country is likely to be very slow to issue a police check, you will have to judge when to request it based on how long you think your country will take to get it to you. The police check must be no older than three months when the Visa Office receive it.
