A great way of visiting Tibet is via India then Sikhim.
I think the best time is September-October/November.
From anywhere in India, fly to Bagdograh, then Jeep to Siliguri.
Get the Toy Train from Siliguri to Darjeeling. Do spend time there, it's a crazy old town, the heart of Ghorkaland.
From Darjeeling Jeep to Gangtok in Sikhim. Awe inspiring mountains descending to Tista river than up to Gangtok.
You can get an Inner Line entry permit/transit visa (15 days) at the border at Rangpo, Sikhim.
Takes 10 mins.
Or you can get a Sikhim visa (6 mths.)or Inner Line Permit/transit permit at the Govt Office Darjeeling, takes about half an hour. Office situated 10 mins walk downhill from Planters' Club, or Keventers etc.
Or, get your China visa in Gangtok, or prior to that at any Chinese Embassy/consulate in India.
Spend time in Sikhim, the local Lepcha folk are very hospitable, as are the Ghorkali of Darjeeling.
From Gangtok, Jeep via Nathula Pass to Giangtse, at the Tibet border.
Proceed to Ljasa.
Or fly from Bagdogra to Gangtok, getting all your permits in Kolkata or Delhi.
I think the overland fro Siliguri is the best value for money and time.
Much more info at this site:
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