I am planning a trip abroad for next year- leaving the UK (I am a British Citizen), and flying to India in around March/ April. My plan is to fly to Delhi/ Mumbai (or wherever I can find the cheapest flights to), and then travel around India for a couple of months or so. After that, I plan to head East, probably through a few of Nepal, Bhutan, Burma, Laos & Vietnam, though I haven't decided an actual route or planned how long to spend in each country.
Having had a look on the UK Government's website about travel to a few of these countries, it looks like I will need to obtain a visa (e-TV), valid for two months, prior to travelling to India, apparently visas are available on arrival at Tribhuvan International Airport and at some land borders in Nepal, while it is advised that you arrange your travel to Bhutan well in advance and that you must arrange your visit through an authorised travel agent.
So, my question for any seasoned travellers out there is: is it best to plan your whole trip well in advance (dates you'll be leaving one country for the next, points of exit/ entry, etc), or is it straightforward enough to obtain the required visas from embassies in whichever country you are currently travelling through?
If it is straightforward enough to obtain visas while travelling, how long prior to travelling should I visit the embassy for the destination country to leave enough time to obtain the visa?