Thanks for the replies @emacdoug @Pierre.
I actually think I was getting some interference. I switched off a wifi repeater on the same side of the hosue as my trainer. I have also recently been experimenting with using my phone as a wifi hotspot (with a view to replacing the sub-1mbps broadband abomnination we get in my ara). I switched that off also and things look a little better. I’ve seen elsewhere comments that wifi can interfere.
My ride yesterday (in TP with no smoothing on the chart) looked like this:
After the wifi changes, today’s ride looks like this (The Trick):
To Pierre’s points, I absolutely agree that it is good to have the real data, not a super-smoothed lie. My demoralised state (perhaps the wrong word on my part) comes from that I (like everyone) want to make sure we get as much out of a workout as possible. Yesterday I really had no idea if I was hitting my power targets at all.
All interesting stuff! Thanks again.