Soft Start Advice

[EddyCurrent]

I would connect the 24v and 5v supplies after the safety relay but before the soft start.
Resistor value is not that critical, you might have to try a few values to get the best for your setup.
That's the maximum wattage, and hence current at the rated voltage, the unit can supply so when it first powers up the load current will be less because the steppers will be drawing very little current.

This seller has some good timers at great prices and keeps some in the UK, then you just need to select a relay with correct coil voltage and amps rating on the contacts. I didn't look through the list of timers but there may be one with suitable contacts already built in, you'll have to look.
timer switch, 60 Sec items in timer store on eBay!