Assuming the pilots do strike, I would expect pretty much the whole BA operation ex-LHR and ex-LGW to stop. The most senior pilots may still work, plus a few other pilots will report for work, who knows at this stage? It's unlikely that BA will be able to charter many replacement aircraft at short notice (given it is peak summer period and also with the ongoing problems with 787 and 737 MAX).
It will be utter chaos. We all know BA's IT can be useless at the best of times, so that won't be much help. They simply won't have enough staff at the airport to process rerouting for everyone and there certainly won't be the capacity on other airlines to accommodate everyone.
So be prepared for a complete and utter mess. It might not be so bad. BA may back down at the last minute. Who knows?
I am not too worried about the 2nd august flight but the 9th seems right into the strike sweet spot (if it happens).
I have not experienced strike related issues, but if I show up at BIO for my LGW-AMS flight I hope they might rebook me to another carrier to get to AMS and not get me to LGW and then stranded. The same on the 12th at AMS to SIN.. If they rebook me from AMS to SIN on another carrier that will work for me. Not sure if they would though.. BA still would have a duty of care (whatever good that does as I would still be stranded).
Globalist