Disco 2 TD5 immobilizer issues

So been out working today.Quick trip 20 miles up M1 and back to a job then parked up at next job only to find once i had unloaded my tools that the car wouldnt lock. Didnt have time to worry about it till i had finished.
Tried to start nothing all dash on as normal all lights went out apart from immobiliser that stayed on unblinking.Took key out to disarm, nothing.It wouldnt arm or disarm no central locking etc Fob lit fine as i waved in in the area of the RF receiver infront of rear sun roof.
To cut a long story short i found the 50 Amp fuse under the bonnet had popped that supplies passenger fuse box along with a couple of others. No joy once replaced.
RAC called out checked all fuses all ok now checked xyz switch think its working ok as LCD display on dash reads right.
Any one had this big fuse pop causing issues.RAC checked fob and said it was putting out a signal.
Looked at RF receiver was dry a terminals clean.
I am thinking a BCU problem.Can they go in such a way as to pop some fuses. Everything else seems to work light fan etc apart from interior light and central locking.
Any ideas much appreciated

and the couple of other fuse where would check connections on engine fuse box for corrosion with the battery disconnected for peace of mind ,assume 50 amp fuse was link 3 would not jump to conclusions as the link feed other items and the couple of other fuse assuming fuse 20 and ?