I can say that that there are currently 21 people booked onto the Vietnam tour in May. Since we don't arrange the regional connections I couldn't tell you whether anyone is flying down from Glasgow though.
As for money it is very difficult to say since everyone's spending habits and requirements are different. I would, however, say that both countries do have ATMs that can be accessed with non-local cards, so that is perhaps the most practical method since you can gauge how much you may need when over there. Otherwise US dollars are the most easily exchanged currency in the region, but also beware that the dong is a closed currency and cannot be exchanged outside of Vietnam (even in Cambodia), so don't exchange too much at once.
I hope you have a wonderful trip with us!