Hi
Yes DVLA just need confirmation number from Customs, there is no charge or fees when declare as this is your own vehicle, so you not trading as business.
Sorry but can not remember about insurance as I have been sent my certificate with all paper work, but as i remember they not asked about this.
The worst scenario just get insurance for VIN chassis number (do not worry about number plates yet) most insurance companies accept this and give you 30days to get UK registration Number Plates (The registration process should not be longer than 14days)
If you already registered with customs, you need to start registration process now as there is limited time.
Thanks and good luck!