Thanks danowat and since you are obviously pretty knowledgeable I'll take you up on your offer and ask another question.
I have set it all up and as a 305 owner for two years I found that fairly straightforward but I am a little confused about software.
Garmin seem to offer two choices, being Garmin Connect or Garmin Training Center. My understanding is that GC is for online connectivity and interfacing whilst GTC seems to be if you just want to analyse your own data on your PC offline. Correct? Then from another thread you seem to be recommending Sport Tracks.
All I've ever done on the 305 is download my runs and analyse them and I think that's all I want to do on the 405, in which case I'm assuming GTC is the one for me? Having said this I'm open to be persuaded of benefits from using either GC or ST. I've downloaded all three of GC, GTC and ST and since I've got an injury and can't try the watch properly (maybe tomorrow) I walked a couple of paces to create a dummy run and connected the 405 to my PC. This was fine and it just dropped the "run" into my old 305 Training Center log on top of all my stored 305 runs. This is what I would have ideally wanted so I think I'm home and dry.
But.................am I missing a trick? Could I be getting more from my new 405, which comes back to me being open to persuasion.
Thanks in anticipation.