I can't seem to advance any further in the Imperial Legion or the Morag Tong.
I'm at Associate in the Morag Tong, have completed all the regular writ quests and meet all the skill & attribute requirements, but when I ask Eno about advancement he just says I need to do more writs. I have accidently prematurely activated the Belt of Sanguine Swiftness Special Job as described elsewhere, but those threads don't describe an advancement problem as a result.
I'm at Knight Protector in the Legion, meet all the requirements and have done every Legion quest save the very last one where you duel Varus Vantinius, but when I ask for advancement he says if I follow orders I'll get all the advancement I deserve or something similar. If I ask for orders he says I need to be Knight Garland rank first. The other Legion quest givers just tell me to go to Varus if I ask them for advancement.
Any ideas or does it sound like I'm SOL unless I console it up?

Have you checked UESP for
Have you checked UESP for quest list of Morag Tong and Imperial Legion?
If yes, type the following in console:
sqv fbmwMTAdvancement - for Morag Tong
sqv fbmwILAdvancement - for Imperial Legion
And post here what it says.