Sorry its taken a while for you to get a reply to your question.
The easiest way to find out is to phone the Court Clerk at the Court where your divorce will be read (Ive found them very helpful and informative). (For some reason, £90 is ringing a bell, but dont take that as a given)
In certain cases, you may be exempt from the fees, if you are on certain benefits.
If you have a Seperation Agreement in place, and all tht needs to be done at the Court is for the Sheriff to read the divorce application and then approve the decree, then it should be fairly straight forward - my divorce (also ordinary) took about 2 weeks from the time it was put to court till the Sheriff approved the decree.