Hi Everybody and thank you for your replies. In answer to your replies:
The car was purchased on the 28th May 2021.The Telematics unit was not activated at the PDI check.
I am unsure how fully or not the battery was charged by the dealer when I took delivery. It as had a few runs out (180 miles) plus a 25 mile round trip to the dealer for the telematic setup on 8th June 2021.
I am unsure if I locked the car in the garage or it self locked after I left it, I only know it was locked when I came to use it on the 17th June and I opened the drivers door by using the key.
The garage is attached to the house and dark, no interior lights were left on, I am unsure about the boot light but after climbing through the car I could not see any boot light switch. I think it comes on if the hatch is opened.
I have been out all day today and not able to chase the dealer except by email which they have not replied to as yet.
I do have a CTEK charger but was reluctant to do anything myself as the car is not a month old yet.
I felt Honda assist should be called out to register the problem but would prefer a new fully charged battery to be fitted rather than a fast charge to my existing battery. After consideration I did connect my CTEK with the battery in situ, Red to positive and Black to chassis earth but after 2 lights light up on the charger the horn kept sounding so I removed the CTEK. As the car was left with the alarm set I think it's Honda Assist in the morning.
I did check the battery voltage with a Fluke multimeter this morning which read 2.44V and this evening 2.33V, a loss of 0.11V in 16 hours.
Hope its not too much of a novel. Thanks for reading it.