Just an update. Incontinence nurse persuaded me to give glycerine (glycerol) suppositories another go. This time I've persisted and they work wonders! Not the most pleasant of things to use, but for me they work in about 10 minutes and then I'm free to whatever I want with the rest of the day. It's just SO liberating! I wish I'd persisted back in 2011 - I could have avoided so many uncomfortable moments and done things I just haven't dared do because of my combined shyness + urgency problems. Hope my experience might help someone else.