Debian :: MAC Spoofing In Jessie Fails

I keep most of my files on my server, but fiddle with them using NFS from one or another of my laptops - so they all have static IPs assigned by my router. If I want extra speed I plug in an Ethernet cable. My old DI524 wireless G router seems quite happy to have two MAC addresses (Ethernet and wireless) assigned to the same static IP, so long as I don't try using both simultaneously. However three Wireless N routers I've tried won't allow this, nor will dd-wrt.

I really don't want to have to set up every laptop as two separate hosts on my network. 'orrible complications.

Best solution I can think of is to get the Ethernet card to spoof the wireless MAC address with e.g. macchanger, as per this excellent page here: [URL] ....

I don't mind running a script manually to do that on each occasion.

This works perfectly on my old R50 Thinkpad running Debian Squeeze, but on my R60 (running Wheezy) and T400 (running Jessie), macchanger works initially, BUT as soon as I hit 'enable networking' in the Network Manager applet, the ethernet card reverts to its original setting. So of course then my router allocates a random IP and so NFS won't work.

Exactly the same goes for the iproute method 'ip link set dev eth0 address [fakemac]' - ifconfig shows it's worked, but it reverts as soon as NetworkManager goes back up.

I don't know where Network Manager (if it is that) is getting the Ethernet card's original MAC from, it seems to be listed in /etc/udev/rules.d/70-persistent-net.rules, so on the T400 (Jessie) I've even tried creating a file in /etc/udev/rules.d/75-mac-spoof.rules along the lines suggested in that archlinux page I mentioned -
ACTION=="add", SUBSYSTEM=="net", ATTR{address}=="[original MAC]", RUN+="usr/bin/ip link set dev %k address [fake MAC]"

but it seems to have no effect.

Short of reverting to Debian Squeeze on all my laptops, I don't know what else to do. Or getting into my router and reassigning the IP / MAC address by hand every time (!).

(If there's a better way to swapping easily from wireless to Ethernet when required, I'd like to know.)