I said I'd post on how the trip went -sorry this slipped a bit - the trip was weeks ago now but thought it might still be worth an update in case similar queries come up in future.
The long and short of it was that the trip was fine, no real problems at all. Perhaps the worst part of it all was the flight out there. I really bloated up and found it quite painful. This was much better on the way back, which I think may have been because I ate less before the flight.
Dhaka was full on, although didn't find it any more so than India. I stayed in a guest house in Dhanmondi - I work for a charity , so 5 star hotels are not an option. But a guest house worked really well for me as it was very friendly, clean and I could eat all my meals there, making special requests if needs be. The managers were also incredibly helpful and I could call them anytime if I needed any help.
Staying in the centre of Dhaka also meant less travel round the city. My colleagues were very accomodating and came to me for meetings as much as possible, also reducing the amount of time I had to spend on the roads. When I did have to travel round the city, again my Bangladesh colleagues looked after me, telling-off drivers for going to fast or taking potholes too hard!
I mainly ate in my guest house, with some meals out. I have spent a lot of time in Asia and other developing regions and since being very ill with dysentry as a student traveller I haven't had any problems, even when drinking local water, eating street food etc. I was a far more cautious on this trip and it paid off as I had no illness, although I did miss the street food. ;) Have to say that I wouldn't have wanted to be there in the first trimester - smells and bad driving would have made me feel really ill.
I guess the biggest issue the trip caused for me was some anxiety beforehand. I did have a few 'oh-my-god-i-must-be-mad' panics in the middle of the night, so anyone doing this kind of trip when pg needs to be confident that they've weighed up the risks and can handle a bit of the unknown.
I don't mean to sound glib and I'm sure there are some MNers who think that just because something didn't go wrong, doesn't mean it couldn't have but I felt on looking at the risks it was worth going ahead with the trip. Overall going to Bangladesh probably isn't top of my list of things to do when pg but I'm glad that i did it and have no regrets.