About to put my disco back on the road after a extensive rebuild and restoration project. Fitted the battery a couple of weeks ago and its been discharging every couple of days . disconnected earth to battery and put a meter from earth on car to earth terminal on battery and got 12v = reading. So I disconnected every fuse till the reading was 0 volts .Turns out to be a 60 amp fuse W-lift/cdl/rear blower. My disco is a 300tdi without air con and a manual gear box mechanical lift pump.
No air con so that rules out rear blower . cdl take it that's for electronic central diff lock (cdl) w-lift is that electric fuel pump . my thoughts would it be ok to remove the fuse altogether And save a load of time searching for the short. Just to let you know while the disco was in storage the mice got at the wiring but I thought I had cured all of there mister meanies.
W-lift Electric windows all working fine
CDR central locking working fine
So I cant remove fuse because windows and doors wont lock and close. Bugger

That 60amp fuse is one of three fusible links, if as you say you have removed the one for the electric windows, central locking and if it was fitted the rear a/c blower these circuits will now be isolated.

so I take it there is going to be a short to earth in that circuit. where to start

Well been at it al weekend.
Disconnected every fuse every relay even swapped relays and every plug and then recheck voltage still getting 12v across earth terminal and earth strap on disco.
The only thing I found and couldn't solve was when I removed earth to o/s headlight the headlight just dimmed and didn't go fully out until I removed the earth on the n/s headlight. Read something about a resister behind windscreen wash tank but there wasn't one there. I now have a put a led across the earth strap and earth terminal on the battery to make it easier to see if the fault goes while diagnosing. But now brain is fried and I need some suggestions and a brake

could the problem be with the mfu has any one had any problems with there mfu?

Why are you testing for volts and not current, milliamps or even amps amps.
Lots of circuits are isolated from their supply as soon as the ignition switch is turned of so removing fuses on those circuits won't tell you a thing.
The multifunction unit along with the security ECU Maurice be faulty but unlikely, the rate of your battery discharging, assuming it was fully charged in the first place, suggests a large current drain which is something that a faulted alternator is know to do.

Brand new 100 amp alternator fitted and power still been drained with alternator disconnected. Battery fully charged with charger over night . Battery good left disconnect and went and checked the voltage tonight and still holding a good charge since sunday . Disco started first turn of the key . and Sunday night we had -15 degrees so battery good . Got a v8 disco outside that I'm restoring next might just nick the mfu of that and give it a go. Did the diagnostic test with the mfu everthing switched on except the head lights.And with the problem I have when removing the earth from the head light .

Think I solved it the light in the ignition switch was shorting out will leave it for a few days and see . No arching when connecting battery earth terminal now.