I Have done some digging and have come up with these as the min MCB's required based on 230V calculations:

24V DC PSU ( Latch relay ) - 3A MCB B type- (345W 230v 1.5A)
24V DC PSU ( Steppers ) - 3A MCB B Type - (460W 230v 2A)
VFD - 10A MCP C type - (1500W 230v 6.5A?)

does that sound possible or would it be more of trial and error ie buy a couple of different sizes and try the smallest that does not trip on power up?

Thanks