MK1 Focus cutting out

Hi,

I've got a MK1 Focus and have got an issue with it at the moment.

The speedo would be stuck at 0 and the car would cut out when coming to lights/slowing down.

Read around online and the VSS seemed to be the issue for people.

I've now got a new VSS and had it replaced but car still cuts out.

Dug a bit deeper on several forums and the next port of call seems to be the ICV that could need a clean/replace?

Any ideas on if this would be it and/or anything else before I spend anymore on this at all?

Maybe useful info:
I've got a DTC code saying battery output is low. (Brand new battery). and had the alternator checked at the garage and thats coming back fine.

Many thanks in advanced!