thanks @brady.miller - really useful facilitiy - i’ll use this next time!!
hi @brady.miller - thanks for the pointer to the stackoverflow article, a slight variation of the suggested solution worked for me - i.e. i put the alternative nameserver 8.8.8.8 at the top of the list, rather than after the existing nameservers, in /etc/resolv.conf.
the updated docker seems to also sort out the other problems i was having. so again, many thanks everyone who pitched in to help.