I'm surprised nobody has replied to this.

I'd suggest some high power Nema 23s motors, or lower power Nems 34 motors. The benefit of using the smaller motors is that you'll generally get better acceleration, and on lower voltage (50V) drives. If you go Nema34, then you really need to get higher voltage (70-80V) drives to get the most out of them, which adds a fair bit to the cost.

I'd do a search over on CNCzone to see what others are using size/power wise, then see what options are available in the uk.