I can't answer your question, I am afraid, but I know we have had numerous threads on cinnamon in the past, so if you do a forum search (search box is upper right side of screen) you may find a discussion on the subject has already aired.
Also, may be worth you having a google. There are a number of websites that will cross reference different herbs and medications for you, and see if they interact.
Here is one: http://reference.medscape.com/drug-interactionchecker
A little bit of online research is needed. I found there are no problems with Metformin. I leave it to you do find out yourself about Gliclazide. Gliclazide does cause hypos occasionally so cinnamon might increase the risk. Good luck.
I've been taking cinnamon tablets (and powder in my alpro soy yoghurt) with no ill affects. It may be that because of this I have got down to pre-diabetes levels. Try and see. I'm on Gliclazide too. Just keep an eye on your sugars.
This http://www.diabetesselfmanagement.com/blog/cinnamon-and-diabetes-an-update/ looks to be a balanced view of it - just bear in mind that if it does have an effect, it's a drug like any other - apart from it having to go through mandatory testing for side-effects and interactions - and, as it says in the article, without knowing what the active ingredient is, it's hard to get dosage right. Also it does contain a substance that's very bad for your liver, so dosage is important.