Mark RushworthYeah, Vietnam is very good. I almost went there but chose Taipei due to their same day approval. You have an employment visa in Australia?
You can apply in Australia if you are a legal resident. Many countries in SE Asia you can apply as a tourist by showing your hotel booking, passport arrival stamp. Singapore you must be a resident. I'd avoid Malaysia as it is the most difficult embassy to apply from. You can get it easy enough back in the UK
Yes, an onward ticket can be required even if you have no intention of using it. Where are you applying? It depends on the embassy. I got mine in Taipei, no onward ticket needed just an intended date of departure.
Can not put a potential return date of 5 years must be within 180 days. Some embassies require an actual ticket of arrival and onward journey be bought, many are ok with an intended date,