vanished international signed for package

[flemmingsjordan]

Hi, I've new to this forum and would be eternally grateful if somebody could help out or just offer advice?

I left my iPad Air and my daughter's Android Tablet on a flight back to Manchester from Dublin (first time travelling alone with my daughter 0 distracted!). My faith on the human race was boosted when a lovely lady at Aer Lingus called me to tell me that they had made it back to Dublin and were at the airport to be collected.
My dad collected and sent them International Signed For (insured to the max of 320 euro). According to the Royal Mail website they were delivered on 27/03/2015. There was (and still is) no signature on the website, I received a ocpy of one via email from customer services though.
There was nobody at the house on the delivery date and no card was left to say it had been delivered somewhere else. I have spoken to customer services several times and have spoken to the delivery office and postman - they have no recollection of the package (which is not surprising due to the number I appreciate).
I have been told that the GPS coordinates on the device you sign show it was delivered on my street - but looks like it may be slightly up or down from my house. Although this may be due to GPS not being that accurate.
I have been to several properties near mine but there is nothing.
My dad has instructed An Post in Ireland to investigate - as I have been informed it must be the sender - although I'm not sure why it is their responsibility considering the tracking clearly shows it made it all the way from Dublin via Heathrow to my road.
I don't seem to be getting anywhere - I have also tried Find My iPhone for the iPad and Android Device Manager for the tablet. Neither show that the devices have been connected to the internet with my account details since they were lost.

Any advice would be so very greatly appreciated!

Thanks in advance.

[SpacePhoenix]

When the tracking number is tried at http://www.royalmail.com/trackdetails" onclick="window.open(this.href);return false; what tracking entries are there?

[flemmingsjordan]

Hi, thanks for the reply. I've pasted the entries from the website below:
27/03/15 10:11 DELIVERED27/03/15 STRETFORD PDO
27/03/15 07:17 ON DELIVERY STRETFORD PDO
27/03/15 06:20 RECEIVED AT PDOSTRETFORD PDO STRETFORD PDO
27/03/15 04:03 DESPATCHABLE TOSTRETFORD PDO MANCHESTER MAIL CENTRE
26/03/15 07:50 RECEIVED IN UK HEATHROW WORLDWIDE DC