I thought £550 for metallic was enough. And does your £625 get you over the ‘free’ colour? The process to paint the car is exactly the same (the exception is Oryx White*) - whether it’s a the solid ‘free’ colour or a metallic colour; the car will get a primer coat, base colour coat and then clear coat. £625 sounds and awful lot of money for what amounts to a small amount of aluminium powder / metal flakes that’s added to a base colour coat.
Having said that, if the free colour is still Urano Grey, I would pay extra for a different / better colour.
*Oryx White; there’s an extra stage in the painting process.