Tldr - did 82 km on the tt bike. 1250m elevation. 209ap 230np. Got rained on big time.
I got up nice and early (as needed to back in time for junior parkrun) for a crack on the tt bike. Wish I hadn’t! 
I’m calling it a learning opportunity, and the reason why we do these tests weeks before the race!
1 - Bta aero bottle thing just doesn’t fit. Tried it anyway as the bts bottle holder I have doesn’t fit the Selle Italia saddle that I swapped onto the bike for this ride - hated the Giant one, so grabbed the one that came with my Canyon. I probs got a max of 150ml out of it! Luckily had my down tube aero bottle with a few hundred extra mls.
2 - front brakes rubbing. Spotted before I set off. Thought I’d fixed it. But there was a much smaller rub evident when I got home. No idea how much this impacted the ride. Probs not at all.
3 - back brake is about as useful as a chocolate teapot. Seriously considered not even starting my ride. But risked it anyway.
4 - garmin mount is totally bodged, as there’s no room for it anywhere else. Will need to get a different type of mount. Turned out it was much more in the way than I’d realised. Practically had to break my wrist trying to change gear. Got a callous forming on my hand from the constant rub.
5 - finally got going. F**king hated it for the first hour. All these things, combined with the crap roads and harsh ride. I was not enjoying myself. Speed was shit. Legs were shit. Head was shit. Wasn’t a happy bunny.
6 - @stenard mentioned in another thread that a 30t may be a good idea for Wales. Yeah, I’ll give you that. Had to grind up in my 27 today. Doable, but not conducive to decent running legs afterwards!
7 - started to just embrace the shittiness and got used to it. Fog about 25km in so thick I could barely see 50m in front. Got a bit nervous. Luckily it was early Sunday am.
8 - saddle came loose. Couldn’t fix it until the 3rd attempt. Was like a see saw slowly tipping to the floor, then I shift my weight and it works it’s way to the sky. Ironically (mostly) fixed it outside a bike shop. It was obviously closed, but a long skinny screwdriver would’ve sorted it in seconds.
9 - started to absolutely chuck it down. By this point I’d perked up a bit and just chuckled to myself.
So a few lessons learned. Lots of messing about with the cockpit required. Need a new hydration system of some sort. Need to consider options.
Also a massive dose of reality, really laid thick - I had hoped to be able to go near a 6hr bike leg. Ain’t no chance sonny on that form. Higher power than I probs should be entertaining, for only 28.5kph. Expectations adjusted.
Sorry - needed a bit of a rant to clear it from my head
(admittedly it was probably about 1K short) but long before Nike shoes existed, and most of today’s aero bike toys.
didn’t feel that wasted although there were a couple of quick food stops and to catchup with the cricket score!