Encountering some problems :-(

Quick update - I put the min pressure up to 10, and my AHI was down to 1.8 last night.
I didn't have time to use Sleepyhead this morning but, from the machine readout, my 90% pressure was 10.5 - so getting very close to my starting pressure.
I also don't remember waking up last night - which may be the first time in about 5-10 years (even when CPAP was going well before the change, I would wake up 2-3 times).
Anyway - thank you everyone who helped - every little bit of advice helped.
I also found 10cms quite tolerable - when I woke up I (as usual) wasn't sure whether the machine had actually turned itself off - but it was doing it's thing quite nicely!
I'll see what 10.5 is like tonight - and then maybe 11. I think by then it'll be almost like a CPAP rather than an APAP!
I also had a fan blowing onto the unit last night to try and cool the air - who knows, I'll try anything!!!
Thank you again - you have all made me smile and skip into the office today

Glad things are getting better. Sleep is a wonderful thing, good sleep that is. Make smaller changes (.5) at this point. You don't want to go any higher than needed, that is where the auto comes in.

I just did a quick review of your thread and the only thing I can add is maybe don't be quite so quick with those pressure minimum increases now that you seem to have things better controlled.
We don't sleep the same each night and the best way to evaluate trends and patterns is with multiple nights with no changes in any of the settings.

So pick a setting and stick with it for a few days before going on to the next experiment. The only time I opt for quick adjustments is when it's blatantly obvious that things are way off base.

I don't have any explanation as to why the obvious change in results with things getting worse when you came home except something changed and we don't know what it was that was changed to cause you to need more pressure for some reason.
The 2 most common causes for rather drastic changes in pressure needs are
1...supine sleeping
2...REM stage sleep
Maybe now that you are home and in your own bed you are getting more REM sleep...
It doesn't really matter...it is what it is and you have to deal with whatever the now is.
The pattern of the clusters hints to REM stage sleep a little. Maybe sleeping a little more soundly now and getting more REM.

I don't think that the leak was the culprit though and I see no need to continue with the mouth taping unless you just want to. During a large leak the AHI during the time of large leak is all that would maybe be incorrect and you didn't have enough time spent in large leak to make that much of a difference.
And yes...taping isn't as bad as one first might think. I remember reading about it and thinking "no way in hell" and once I decided that a chin strap wasn't working well I did the mouth taping and found out it wasn't nearly as bad as I thought. I quit taping about 3 months into therapy once I realized that the mouth stayed shut for 95% of the night and the other 5% I slept right through it anyway.
Now if you find that mouth opening disturbs your sleep...that's a different story.

I doubt there is anything wrong with your new machine but you could use a manometer to verify pressure output for your own peace of mind (or maybe the place where you got the trial machine has a manometer).
It's fairly easy to make your own homemade manometer (search the forum for past threads) or they can be purchased for not much money.....but I would see if the place where you got the trial machine would do it for you for free because those places will usually have a manometer on hand.