A4 B5 2000 Instrument Cluster

Electronic issue please help, after months of checks and invesagations called out a mobile auto electrician.  Battery drained on my beloved 2000 audi a4 b5.  After this the problems started but are intermittent. Instrument cluster only part or not at all lighting up and guages the same, mileage doesnt appear when unlocking car.  Immobiliser kicks in and stops the engine running after a few secs.  Every now and again the issues will change with the car starting but not all guages working then next start back to immobiliser kicking in.  Replaced the battery, found an apparent power drain on fuse 15 relating to cluster. Auto electrician plugged in diagnostics and coulnt read/communicate with the cluster so advised it was faulty. Anybody had this before or advise if sending cluster away to be tested repaired is best next stage. Many thanks Chris Glasgow