These guys C & C Marine at Largs do equipment hire and boat trips, I dived with them some years ago, the Clyde wrecks can be pretty dark. 
Don't write Oban off for a weekend, 2 hours isn't that far and can certainly be done either for a day or weekend.

Don't write Oban off for a weekend, 2 hours isn't that far and can certainly be done either for a day or weekend.