A survey is carried out prior to any installation, and - from when I had mine done - it seems to be that any potential problems concerning the house and whether it is suitable are sorted then. In other words, they will tell you what is suitable/ possible.
If you can get it done it is worth it - I used to have to have my heating on near enough constant in winter, but since getting it, I use it to heat the house for a short while and then turn off, and it retains the heat for ages. Coupled with draught proofing, it's more than paid for what I did have to spend on it.