What are you asking?
Any flight finding app will find flights and fares for you. For the three most commonly used domestic carriers go directly to their websites.
Vietnam Airlines, Vietjet, Jetstar
Be more specific with your questions, then TA members can help.
If you want to find flights, use Skyscanner and book directly with the airline, not an agent. Why? If you have to alter your flight details, agents charge exorbitant fees.
Go to Travelfish.org for some in-depth research to find out which places are likely to best suit your interests and preferences.
We all have differing ones, so a post like yours which is so open is more likely to lead to confusion rather than help.Edited: 03 August 2018, 23:11
Agree with the post above!
I slightly disagree with the above, Travel Agents in Australia (generally) offer a great service, if you do all your bookings online
and you have trouble I have heard others say they cannot contact the appropriate third party, to each their own.
As far as Hoian, no problems, you will enjoy your stay there, it is coming off their wet season so you may get a cooler
day here and there but generally it will be ok.
First off it is my opinion that you should not entertain booking with a UK Travel Agent. By all means get your flights booked as per advice above and then armed with your dates research on this forum for Vietnamese Agents. Any main street agent in your home town will not be traveling with you, as they are merely subcontracting a Vietnamese agents Tour, so you may as well get the same tour and save yourself a bundle.
Just book your flights direct with the airline,and your hotels with one of the usual hotel booking websites
The days of paying a travel agent to do this for you is long gone
Take a look at Kayak to find flights that suit your requirements then book directly with the airline.
Hotels can be booked on Expedia, Booking.com, Agoda, etc, etc
I usually book Direct with th airlines concerned. Start by looking on Kayak.com for International and internal flights.
If Trailfinders can’t help then STA Travel are very good and can sometimes get better deals than booking direct.
Booking.com is good for accommodation.
Basically, you need decide where you want to go, what you want to see/do to sort out an itinerary. Buy a guidebook and have a good read. I like Rough Guides.