So I made extra time this morning and went to pick up Heart Gold from the post depot. The box is indeed similar to the Walk With Me (Personal Trainer Walking in the USA) game so explains why it couldn't fit through letterbox & this first 30 mins (ish) replaces the time missed yesterday.
After the usual brief introduction and naming ceremony (I am a Girl named 'Retail') I rushed in to see the man in the lab coat and got given a Pokemon - I chose Totodile as it was the first one I clicked on & named it 'DeeArrEmm'.
I rushed out into the grass to find Mr. Pokemon, roughly remembering where it was from the olden days and killed a few 'Mon on the way with scratch. I chatted to him then ran back down (getting various bits of tutorial and gear) and met up with the rival (who on returning to the lab I named 'Piracy'). I finished off in starter town and made my way back to the original town - getting pokeballs off Ethan on the way.
Casual rules state that I'll catch the first Pokemon I see so now have a Pidgy ('DLC') and a Geodude ('Bricks') which I found on the way. I made it to the PokeCenter and put them both in the PC so I could at last use the PokeWalker - 34 mins in.
On the walk back Bricks already levelled up, so I flipped him out of the PW and then put him back. Not sure how this is going to effect the watts and moves that they learn - will find out the hard way no doubt.