[0l0dom0l0]

Good progress. I would hold off on the injector(s) for the moment. It takes a while for the long term adaptions to be re established and it is very common various codes indicating misfires etc come up (which I assume is what they are referring to) in the process. I have had this myself after reseting the adaptions. Car is now absolutely fine. So just give it 500 miles or so before you pull the trigger on those. There is a stack of information on binmerpofs if you want to read up on it for yourself.

Fuel pressure sensor is easy enough to do. The low pressure sensor can be accessed by removing the throttle body and airbox and there is no need to take the whole maifold off. A 15 minute job and the sensors are not expensive. High pressure sensor is a 15 minute job also.

Not great news about the water pump although they are not stupidly expensive these days, especially the pierburg ones. As you'll probably know it is worth doing the thermostat at the same time. I would get the genuine BMW stat but that's just me.

[doggy]

Thanks, I appreciate the advice and benefit of your experience. I'll give it some time to bed in, (& hopefully get diagnostics working so I can monitor properly).

He did say it was the low pressure sensor.

Initially got scared off a DIY water pump change, but having watched a few videos I think it's doable. Agree it'd stupid not to change the thermostat for an OE one at the same time. I'm looking at this as a worthwhile preventive maintenance operation so not too upset about it.

[doggy]

A little more progress, I now have ISTA communicating with the car, just have to find out what it all means.
It's also survived a few downpours with no apparent ill effect.

I guess checking the drains cope during heavy rain is an E9x rite of passage.