I am signed up to my second marathon on the 8th of April and my first ever half ironman on the 17th of June. To answer questions of fitness/experience, this marathon I'm aiming for around 3h30 mark. This will be my first triathlon of any kind, but I am a pretty competent swimmer. Currently on a training programme (bupa advanced marathon programme) of 5/6 runs per week for the marathon but this doesn't involve any swimming. I cycle every day about 5 miles to go in/out of work, so cycling is the least of my worries (I have completed cycling holidays of around 70 miles a day max so have experienced of longer cycling).
Any tips for the transition to the half iron man training, whether I should implement some swimming earlier into my marathon programme for the steadier runs.. any tips for a programme, any particular sessions, a good way to transition, etc.