Overseas licences.
If you learned to drive in a country that is a member state of the EU, then you may legally drive on that licence until the expiry date shown on it, or three years from becoming resident, whichever is sooner. You do not need to take a UK test, only exchange it for a UK full licence. But, if you are going to be in the UK for a reasonable length of time, you may find it is cheaper for you to insure your car in the UK if you have passed a UK test. If you have a licence from outside the EU, then you may be able to drive on that licence for a maximum of 12 months. If you take, and fail, a UK test, you are no longer allowed to drive in the UK on your foreign issued licence regardless of how long you have been in the UK.
The rules on overseas licences are complicated, and this is only a guide, so please check on the link below to ensure your licence is valid:
http://www.direct.gov.uk/en/Motoring/DriverLicensing/DrivingInGbOnAForeignLicence/index.htm
I have a lot of experience in getting people with non-UK licences through the UK driving test. As a general rule, this is simply a matter of tidying-up any bad habits and ensuring that a person knows what to expect from the test and what the examiner expects from them. Before a pupil can start their lessons, I will need to see a current UK provisional licence. This is because I have no way of confirming if they have been in the UK for more or less than 12 months. They will also need this licence, plus a theory/hazard perception test pass, to book their driving test.
If your company is paying for your lessons, I can issue receipts for each lesson payment received.