UK C180 electrics

C180, Year 2000, 2000cc
A couple of days ago I could not operate the remote central locking and had to get in via the emergency silver key. The remote part would
not "engage" with the key slot on the dash. Discovered that I had no voltage from the battery. (interior lights weren't working). Lifted the bonnet and found the neg battery terminal loose. Tightened it up and car started but now I have a malfunction warning on the dash, wipers don't work, fuel gauge does not work, indicators and hazard lights don't work.
Dealer cannot look at it till next week and suspects that there may be a fault with some unit that links into the ""can bus system??""
Has anyone any ideas what could be wrong and how to correct it?
Regards Graham

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