At the moment, when you go into Point of Sales and display Loan cars, it displays the vehicles in the default location setup in individual users GB.location
There is a new parameter which allows you to default as per POS branch(if you have multiple POS branches) or default as per Point of Sales Department.
Note:
If a location code is set on the SO.depts record it will be used first, otherwise it will look in the POS parameters.
First, you need to enable the parameter in MS>X4>Generic CRM parameters>
Tick Loan vehicle filter by department/customer

POS Department option
POS>Misc options>Department codes

POS Parameter option
Need to setup in each POS company
POS>system maintenance>POS parameter>Flags and priorities>Miscellaneous TAB

Note that this also affects when making a loan car booking within CRM, in there it will use the creating branch from the CRM customer record.