Tobago is a wonderfully unspoilt and under developed island and this means tourists but not many. As a result there are not lots and lots of flights. British Airways and Monarch fly to Tobago from the UK. Please see below for details.
If these days do not suit then the other option is to fly from the UK to Trinidad with British airways and then to catch the local inter island flight over to Tobago which takes approximately 15 minutes and costs around £30.