Speedo/BSI problem

[Romahomepete]

3 years ago the instrument cluster on our year 2000 1.9 Berlingo went kaput, temp and fuel gauges stopped working the rev counter and then mileometer went to 600000 and stuck. Tried a couple of second hand clusters but they had faults and so lashed out on a new cluster (needed a mortgage), everything is working file except for mileometer which still says 600000. We hav put up with it for all this tome but now the other half would like it fixing. The local Citroen dealer says that it can be fixed but they will not fix it because of the problem of "clocked" cars. Apparently the mileage is stored in both the cluster and the BSI and the 600000 is a Citroen default when things go wrong. Does anyone know of a fix? can this be put right using Lexia. We are willing to pay if it can be done.

Peter