I think its best to discuss this with your GP and consultant at the hospital to get the best answer. Hospitals vary in their policies, so what one does, another might not.
The general understanding is if you have had an emergency C section, depending on why is was an emergency they will consider a planned C section for the following baby. However, some hospitals now seem to prefer (unless there is a genuine reason to have another C section) to try for a VBAC in the first instance and then if need be to have a C section. However, if this was the main option given to you, you would at least know that a C section may happen.
Also you have had well over 2 years between your C section and having another baby so a VBAC is considered a good option as the wound is well healed etc. Pregnancies too close together can present a problem for pregnancy and delivery.
As for how many C sections you can have safely.... my understanding is the more you have, the higher risk for following pregnancies due to the incision and so on. Pregnancy puts a strain on everything and can cause damage and need medical intervention if the scar suffers damage. Eventually it won't be safe to become pregnant anymore (if you have lots of C sections) as each time they go in via the same incision as before, and in the end the tissue damage etc is too much. Hence them now preferring to try VBAC in the first instance where possible.
They cannot 'make' you do anything, but they will advise you of your options. However, I'd think carefully about planning a C section if they think trying for a VBAC is something you could do. Also remember your second pregnancy may be very different from your first and make a natural delivery a much better thing to try. Also if you did go the VBAC route and did need a C section for whatever reason you would be much more prepared and so would the Doctors as they would know that delivery had a chance to end in C section.
Keep an open mind and when you are PG you can see how your pregnancy goes and discuss with the Consultants nearer the time.
Hope that makes sense.