Wouldn't use any sort of gag if she is already putting her head up, they have a raising action. Use a gentler bit that she is not afraid to take a contact with. Hate a martingale myself, as soon as it engages you've lost the straight line to your horse's mouth. I've had best results with copper...
Much more limited range of fittings with synthetics so that must be your first consideration. I find my Wintec good for riding position. Prefer the CAIR panels as they have a less convex profile and settle better onto horse's back. Still prefer leather but I LOVE my plastic job on days like this!
I agree that this is a price for a 'made' horse and as he is 6 years with no previous listed it does seem steep. You are paying for the colour of course!
I emailed Emma Rushton in Dec via link to alternative site - she was having a nightmare with new website but hoped to get it up and running soon and membership pack to me in the new year. Have been popping on to the original site to view the forum (like you can't join in until membership!) but...