@MB72 You are entitled to your money back. At no stage do we ever enter into a legally binding contract with a dealership. The only contract is between you and Motability Operations, and even that doesn’t come into effect until you enter the PIN on the day that you take delivery. There have been occasions in the past where one or two dealerships have played hard to get about refunding deposits, but by quoting the above people have eventually got their money back.
As others have said, the adverse changes to Motabilty don’t come into force until next summer, so you won’t be affected with this car. However, you might decide to source a car privately now if you think that you’ll leave the scheme after just one car, so that you continue to own a car and have a deposit next time, but only you can decide which option is right for you.