Jimm...please tell me...if you leased a brand new car..would you find it acceptable it was only firing on 2 or 3 cylinders on a regular basis? I can guess the answer. I'm on a 5-car 800 travelling along your beloved Cotswold line and hey..all 3 engines are working - hooray. And actually my position in the coach (seat 46 ) is quieter than my previous 800 (your seat position in relation to engine location does make a difference). So..so.e good news to report. Yay. But i still do not agree the quantity of engine failures after 18 months is acceptable - even of they are not serious to cause services to be cancelled frequently yet.
You're the one making claims that engine issues on IETs are regular, indeed so widespread are they that the installed power, you tell us, "is rarely available" - which hardly tallies with the very clear improvements in reliability and punctual operation across GWR, and not just in places where the IETs are running on electric power. But apparently we can look forward to frequent cancellations soon...
Where exactly is the statistical evidence to back up what you are saying? Or are you just going to adopt the tactic favoured by some here of making the same claim over and over, without any supporting information, bar the odd anecdote, in the apparent belief that if it is said often enough, it will eventually become the truth.
If Cotswold Line IETs were suffering crippling engine problems all the time, then they wouldn't be arriving in Moreton-in-Marsh from Evesham early after climbing Chipping Campden bank. Or waiting time at other places, day in, day out. Same goes for services on other GWR routes.
In case you are forgetting, HSTs - that would lose lots of time on that climb when running on one engine, especially on a dank morning with slippery rails - suffered a protracted period of engine problems after they were first introduced.
Maybe GWR just take a note of the (fairly random) days and times I am using their trains and make extra-sure that mollycoddled sets with freshly overhauled engines are laid on specially for me both ways, so they don't ruin my love affair with Class 800s...