You will most likely be UNABLE to take your test in a Left-Hand Drive Vehicle in this country. The 'Hand' of the vehicle is only different as a result of driving on the opposite side of the road.
Passing a test in an Automatic car will allow a person to pass their test alot quicker than it will to pass in a Manual. Also, insurance premiums are lower, but running costs are higher. You are right in assuming that you cannot drive a manual with an Auto licence.
The Manual Licence covers much more than the Automatic. Automatics cover the basic road safety and driving techniquies, but manual goes further by teaching you clucth control, gear change techniques and much more.
Manual Drivers can drive an Automatic.
Passing in a Left or Right hand drive car will make no difference, but to pass in a left handed car, you would have to pass in a country that isn't covered by the DVLA. Once you have passed, your licence would be valid in this country for 12 months, after which you would be legally required to obtain and Internation Drivers Licence.
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It seems that an International Licence will run you a fee and you won't have to sit any tests. You could also swap a foriegn drivers licence for a UK one, but the Foriegn Licence would not be returned, essentially meaning that you would need an International Licence after that in order to drive in any other country for a period of time longer than their acceptance of a UK Licence.
Country Specific Requirements (IDP)