Is this error code displayed immediately after power-up, or after some time using the welder?
If the latter, does it happen in both MIG and Arc ( MMA ) modes?
If you search for "inverter repair" using the box on top right you will find some general troubleshooting hints.
Tec-Arc in York offer inverter welder repairs.
You could also try contacting R-Tech in Tewkesbury. They service and repair their own machines, but also offer repairs for other major brands.