You say 'MoT to August 2015' - from this it must mean that the MoT has expired, therefore it DOESN'T have an MoT.
I read your post as the car was MoT'd in England in August 2014 and sometime later exported to Spain. If you have an ITV to September 2016, then it must have been ITV'd in Spain in September 2015 (last month) and should be on Spanish plates. If this is the case, it is legally a Spanish car and any UK documentation is irrelevent.
If you're not sure, this is one of the times when you should really go to Traffico in the area where it is registered and get it checked out.
Steve