Have you checked out pieces by Telemann? His Fantasia in D- TWV 33:2 as well as his Solo in F+ TWV 32:4, (the bourree) are quite nice and are around intermediate from the RCM syllabus (grades 8 and 7, respectively). If you are looking for a late intermediate/early advanced, RCM 9, piece I like and played the Scarlatti Sonata in D major K430. However there is a vast number of Scarlatti sonate this is just one suggestion, so you can check the other ones.