20 miler in March, would give you 3 1/2 months until Cotswold so should be fine. Training plans will have you running 20 milers, so a good test. Anyway, not much fun putting all your eggs into one basket and not really enjoying the build up.
Ticking along nicely. Swimming is OK and lolling to start increase the frequency. Biking going well, high RPM sessions on the gym bike, and good road rides on the singlespeed. Running OK, 20k is longest to date.
Hoping to cycle the course in late March just to get to know the course, and then focus the training to suit.
Camilo, don't worry, your swim endurance will build quickly, and 3.8km will be do'able, and you'll have swum it numerous times in training. As to sighting, when it's warm enough just get out in the open water and get used to it. The more you do it the less anxious you'll be.
I've been in the pool 3x now, no more than 1km each swim, and mainly drills and breastroke, but it'll start building soon. Running and biking often, but with no real structure yet, but walking lots, generally active and trying to eat well