Tri / Triathlon / Triathlons - do they float your boat?

Will have 6 hours to myself every Friday (term time) come September. Going to use that time to get fit again (as well as work gym bike intervals, cycle commutes, midweek 5-a-side and other runs). This will involve cycling (Richmond Park mostly), swimming (local council run swimming pool) and running (local roads and Parkruns at the weekend).

Long term (2016) goal will be a Triathlon (either Ironman or ease into it with a 70.3 first).

With 6 hours I reckon I can build up to do a 1/3 distance Ironman (given the transitions will be a bit longer than normal - it's 1km from pool to home - and I can't just dump a pile of stuff at the pool). Something like:-

9.15am - get to swimming pool after dropping MiniGB off at school
9.30am - start 30m swim
10am - out of pool
10.30am - changed and home from pool, quick snack
10.45am - out on onto bike
2.5 hours for the 60km to Richmond Park, 5 laps and then back home (eating lunch whilst on the bike)
1.15pm - home, quick change
1.30pm - out for 14km run (1h20m at 10.5kph to begin with)
2.50pm - arrive a sweaty mess outside school gates ready to pick up MiniGB

(Very conservative estimate for the bike ride, I should be able to get that down to under 2 hours within a few months. That'll give me enough time to finish the run at home, shower and then amble down to the school.)

Won't do that every Friday. Different day structures could be:-
a) Cycling hills: Quick blat out to Surrey Hills, 50km hilly route and then train home (or cycle if time)
b) Longer swims (build up to 1 hour and beyond, work on speed too) and then either run or cycle
c) Longer runs (outside) building up to half marathon distance
d) Speed work (running) on a treadmill at the gym
e) Or just doing two of the three activities

First job will be to gauge current fitness and start shedding some weight (have ~15kg to lose).

Swimming: Haven't done any meaningful swimming for years (I take MiniGB every week but I can't leave her in the pool whilst I do lengths!) Latent technique after years of being coached though. Pool has swimtag so I can get some geeky stats on efficiency/etc.

Running: Will be building up running on Monday and Wednesdays in lunch break too. Even doing a 5k when carrying 15kg extra is hard work.

Cycling: Least of my worries fitness wise. I do ~80km a week cycle commuting but not fast. The legs (and head) have memories of the long distance (Audax) stuff from a few years ago so hours on a bike doesn't phase me at all. Once weight starts to come down I can shift some focus to intervals on a gym bike to boost power.

Can't wait to get started on it.