Thank you very much and others for kindly posting their mistakes and tips. Mine went in during September, it took half a day, and has been keeping my 25m2 garden office toasty through this winter. Looking at saving around 800-1000 kWh over the course of 12 months over resistive heating at this rate.
The installation, vacuuming etc. was all easy enough after watching several hours of YouTube and reading these forums. I'm still paranoid about the flared joints, but that's only because I've read the horror stories and didn't have a torque spanner - although I've got 35 years experience in fixing up bikes/cars to have a good feel for tightness.
The remote control however has gone, and Appliances Direct say that they can't provide a replacement, as it's obsolete. So they've offered me a partial refund to buy a compatible alternative - that doesn't have some of the functionality. I use the Tuya interface so not a major issue, but I do need the remote for the rest of the family when they use the office...
The Tuya functionality is great, I've created three scenes to switch the heating function on early depending on the outside weather: <0, <5 and <10. Still playing around with this but <0 switches the heating on at 0500 which is enough bring it to 18c from an indoor temp of 7c by 0900
