I would have loved to have found a dressage saddle for that but don't think they exist. I had to buy a new Albion platinum job, the price was shocking but it is great, a secondhand one of those would be a worthwhile purchase.
I recently bought an Ideal Suzannah within your budget. I have been so pleased with it. It is well made, extremely comfortable and positions you nicely.Ive also noticed my horse is a lot freer (sp?) across his shoulders and goes really well in it! To look at it you would think it was an albion. Ive popped a link on the bottom of this post with pictures and a little description. Hope this helps!!
I like the Bates Isabel Werth ones. They are very comfy and have the adjustable gullet so they fit a wide range of horses. However, they are £1,200 new. Perhaps you could find a good second hand one on ebay?
Alternativily, if you got a saddler out to find the best make and size to fit you and your horse, you could buy a nearly new expensive one off ebay for a fraction of the price! (An if you needed a NM one, I may just be able to help!