Considering how many people drive around out here with no rego, no insurance, bare tyres - I even read about someone who had no glass in his windscreen and was driving with a molegrip on the steering column because he had no steering wheel - I am sure the police will be totally forgiving of you missing the deadline by a few days/weeks. They're not stupid and will be able to tell you're not a brazen criminal. I think the worst that will happen is they'll check, and if you haven't got the rego in your hands, give you 48 hours to bring your documentation along to a local policestation, check it then and then forget all about it.
Please don't worry - I work on the basis of not wasting energy worryng about something you can't change, and you've done everything you can now, so don't suffer any more stress.
Sending you virtual hugs anyway!