The more important question should be, what exactly does it say on your Motability paperwork and particularly the RSA Insurance certificate?
What does the badge on the back of the car say it is?
Is there any difference, performance or engine wise between the two and are both available on the scheme (Titanium and ST line)?
There was a thread on here recently where someone had been given the wrong vehicle (a Mercedes I think) which caused all sorts of problems, but I think was eventually resolved by senior management at Motability.