Tourist E-Visa Vs "Paying at the door" at Siem Reap Airport

I'll get some passport photos done - and will take with me - and if I don't need them - will use for my next Visa application to another far flung land.

As an off topic (a bit) - we have just discovered you cannot purchase Cambodian Riel or Vietnamese Dong in the UK ... probably because of the amount of notes that equal £1 .... so we'll be taking dollars - and changing up when we reach each country. Guessing that's the right way / only option .... am I correct Viet/Camb experts?

Know any good outlets in the major cities - non-rip off merchants / scammers - or best to just use our hotels or local banks to get some local money for the smaller purchases / just to experience the real money. Thanks in advance.

Charley x

You do need to bring USD to pay visa fees for both Cambodia and Vietnam. Strange as it seems Cambodia uses the USD for many/most larger transactions, and the local ATMs give you USD. You'll get Cambodian Riel back in change of less than a dollar or so. For Vietnam you can get VND (Dong) from ATMs, or change GBP for VND at banks, or many gold shops. Other than for visa fees, you do not need to change your GBP for USD before you leave, use ATMs and save yourself the exchange fees.
Cambodian Riel and Vietnamese Dong are non-convertible currencies. That's why you can't usually buy them outside their home country, and once you leave their home country it's VERY difficult to exchange them for any other currency.

I cannot understand why in 2014 travellers would consider taking large amounts of cash with them instead of using ATM's ok I know that you will be charged a fee but surely this is much better than taking the risk of loss or theft. I am old enough to have travelled in the days before ATM's and spent four months wandering Asia with a money belt stuffed with travellers cheques which could on occasions be extremely difficult to cash and subject to a huge commission rate also large amounts of cash. One of the biggest problems was when you wanted to go swimming, what the hell did you do with your money belt?