Thank you for the replies everyone. Appreciated.
First off, the motivation for the original post wasn't to afford me to sit and criticise the replies. That's bizarre. Especially since I've only replied once in the whole of the thread and not sat ripping into individual responses. Yep, the question was asked on another cycling forum. I thought I'd have some luck there too, and gave the basket weaving websites and mumsnet a miss :-)
I'm sorry some of you have found the question "pointless". I asked for recommendations and was hoping to get some useful pointers equally on what to avoid and draw from the experience of others rather than just recommendations. I don't expect anyone to choose for me or validate my choice. But thanks goes to those who've helped and wished me well.
The Ironman is likely the last I'll do, instead I want to focus on more bike specific stuff in the future. The course next year is very hilly - 8000 ft of climbing I think - and a TT bike isn't likely to be any real advantage on the day. Next year's trip is booked and paid for, so that's not a consideration. And future trips / cost is something I'll be OK with in the future and don't need to budget for, all being well.
Canyon bikes are great value but with it being internet only I'm concerned about not getting the sizing right. I'd need to sit on and try out a few bikes to ensure the fit's spot on. So unfortunately they're ruled out.
Componentary and groupsets, although wheels excluded, seem much of a muchness at this sort of price point, so it's all in the frame and how it feels/rides. The only way to know is to try them out, I guess.
Thanks again.