Is there a way of emailing one call up per job on separate emails? 

Yes there is, per supplier you can configure how Emails are sent or how Faxes are sent:
Please see screenshot below on how you can configure this for your suppliers


 The Message and Email group options are:-

1 Session Per Message - Each call out “session” is dispatched

1 Session Per Contract – All messages for a contract go out at the same time.

1 Session Per Day – All call outs for a supplier for that day go in the same message

1 Session Per Day – 1 Page Per Message – As for the previous except a new page for every message

1 Session Per Supervisors – A separate message for each supervisor