Why should there be a problem if its defineatley LPG .The only one I can see if it was converted to run on propane or earth gas as in German conversions because I don.t think there are any earth gas stations in the UK.
I am not sure but do I need to provide certificates when reregesterung the car or when the car comes to being MOTed, then what info will insurance want, will they accept t if it is in Spanish