Err, not sure about advice. My original plan was IMUK last year, a couple of months rest, then build over winter for IMNZ. The reality is become injured, put on weight, become more injured, do no races, have Christmas and start training in January.
I'll let you know how it worked out in 48 days time!
Not sure where you're based, but if in the UK then the last Middles are in September (Vitruvian or Accelerace Extreme in Devon). Both good challenges and will set you up for winter I'd say.
I think I'd suggest you focus on the cycling this year, and then bring in more running and swimming over the winter. The reason for that is that it's pretty hard to do the long rides at this time of the year (or at least be able to do them with regularity and the safety that you're not going to fall off on ice / in winds and pick up an injury. Working on the running and swimming is not without dificulty, but easier than the cycling. I'd suggest that you plan a rest after September for a couple of months where you'd do nothing serious, a few classes, a few jogs, the odd weekend ride with friends. You'll need that mental and physical break as otherwise you'll burn out in November and that's going to be more detremental.
Practicalities, then the flights get released in April time I think, book early to save money. Plan to go via LAX as that gets you a better baggage deal if you're taking your bike and the rest of your kit.
Obviously I'd be more than happy to comment on the details of the race once I've been.