Have done a couple of observations now and uploaded to ExoClock. The HOPS software is good and relatively simple to use, but I’ve discovered a slight flaw: If you choose a comparison star that is saturated, the software crashes. Have been in touch with the developers and this will almost certainly get resolved.
Obviously there’s no point in choosing a saturated star but if you do it by mistake (as I did) it crashes. There’s no facility to check the levels of the stars you selected yet so I used the AstroImageJ seeing profile tool. Hopefully something will get added to HOPS to avoid mistakes in future.