My only comment is never trust a main dealer, its very rare they actually know what they are doing with the berlingo, this is verified with the fact they couldnt understand why the fault light kept coming on
As others have said either get a EVlite or more expensive Lexia unit, DAIG 2000's also will do the job along with Planet systems
Regardless of what the dealer has said they have done I'd personally check it out, brush checking is really easy, also it would be interesting to see what the current over charge Ah meter is reading (can be seen with an EVlite etc) as I wouldnt put it past the dealer to randomly reset paramiters in a vain hope that it will clear the fault
The risk with this is if they have reset the overcharge Ah meter without doing a watering maint charge you could end up running the batteries over the recomended Ah overcharge rating without watering which can/will damage the batteries.
If you suspect they might have done this then I'd carry out a maint charge and watering on them, but this of course MUST be done with the EVlite or other diagnoise unit
ChrisB