Hi Scottish69.
I had the same problem you currently face.
I purchased my GTI last September for a March delivery (06 plate). Although I was a loyal customer (previously purchased two other vehicles), I got no discount, despite spending a few quid short of £26K.
The only thing I did get was book price for my 4-Motion. I only got this because the dealer agreed this prior to me paying the £1K deposit, of which they had for nearly 6mths!
Although I would be surprised if you got anything off the GTI & options, I would have expected your dealer to offer you Glasses guide valuation for your Celica.
Until the GTI loses it's appeal, dealers are unlikely to offer any discounts. Why should they! The only alternative is to look on the internet, but you may find the vehicle is an import. Personally, this did not appeal to me as I would prefer dealling with an approved dealer.
I have noticed the price has slightly increased over the last few months. When did you place your order?