Salford Triathlon is a good one to start, that's obviously if you're local. Plenty of them though mate, just start with a 1000m swim, 25mile bike and 10k run. You can even find smaller tri's or Duathlons if you want to get started on it.
This will be my first Ironman so looking forward to it but with some trepidation......
Cheers Inchy - heard the Salford one mentioned a few times so I'll def look into it. Do you tend to require your own bike (I have one but it's a basic hybrid that I haven't ridden for some tome) or can you hire on the day?
Good luck with the Ironman...incredible feats of endurance but I'm sure you've put the time and research in.