Is there any way to configure the options that Network Manager sends to dhclient?

[Chris Green]

I'm running xubuntu 17.10 on my laptop (soon to be 18.04) and use the
default Network Manager to handle network connections.

I have a need to change the dhclient settings which are set by Network
Manager which calls dhclient:-

    chris$ ps -ef | grep dhclient
    root      7586  1585  0 09:00 ?        00:00:00 /sbin/dhclient -d -q -sf /usr/lib/NetworkManager/nm-dhcp-helper -pf /run/dhclient-wlp4s0.pid -lf /var/lib/NetworkManager/dhclient-aa408c06-abb7-467e-a228-f8b35a4d9222-wlp4s0.lease -cf /var/lib/NetworkManager/dhclient-wlp4s0.conf wlp4s0

In particular I would like to be able to specify the lease file.

It's obviously not set in /etc/dhcp/dhclient so is it built in to the
Network Manager executable (I hope not), or what?

-- 
Chris Green