I have created a workflow in process builder to map a picklist field from a custom object into a contact object. I can successfully map other picklist fields but this one gives the above error. The only thing I can think of is it might be too long, the picklist is UK counties. I'm using a global picklist so I know that both picklists are identical. The error message is below. Grateful for any ideas. I have 3 other picklist fields that failed too, one a multi-picklist, but I'll tackle those later.

RECORD CREATE: myRule_1_A1
Create one Contact record where:
Birthdate = {!myVariable_current.Date_of_Birth__c} (06 July 1996)
Charity_Referrers__c = {!myVariable_current.Charity_referrers__c} (null)
College_Referrers__c = {!myVariable_current.College_Referrers__c} (null)
County_of_origin__c = {!myVariable_current.County_of_origin__c} (Berkshire)
FirstName = {!myVariable_current.First_Name__c} (Test)
Gender__c = {!myVariable_current.Gender__c} (Female)
LastName = {!myVariable_current.Last_Name__c} (Dodd)
Local_Authority_Referrers__c = {!myVariable_current.Local_Authority_referrers__c} (null)
MobilePhone = {!myVariable_current.Mobile_Phone__c} (06610230804)
Next_of_Kin_First_name__c = {!myVariable_current.Next_of_Kin_First_Name__c} (null)
Next_of_kin_Last_name__c = {!myVariable_current.Next_of_Kin_Last_Name__c} (null)
Previous_accommodation__c = {!myVariable_current.Previous_accommodation__c} (null)
RecordTypeId = 01258000000U464
Referral_Agency__c = {!myVariable_current.Referral_Agency__c} (null)
Social_Services_Referrers__c = {!myVariable_current.Social_Services_Referrers__c} (null)
Town_of_origin__c = {!myVariable_current.Town_of_origin__c} (Slough)
npe01__HomeEmail__c = {!myVariable_current.Email_address__c} (dodd@gmail.com)
Result
Failed to create record.

Error Occurred: INSERT --- INSERT FAILED --- ERRORS : (INVALID_OR_NULL_FOR_RESTRICTED_PICKLIST) bad value for restricted picklist field: Berkshire, 

I have created a workflow in process builder to map a picklist field from a custom object into a contact object. I can successfully map other picklist fields but this one gives the above error. The only thing I can think of is it might be too long, the picklist is UK counties. I'm using a global picklist so I know that both picklists are identical. The error message is below. Grateful for any ideas. I have 3 other picklist fields that failed too, one a multi-picklist, but I'll tackle those later.

RECORD CREATE: myRule_1_A1
Create one Contact record where:
Birthdate = {!myVariable_current.Date_of_Birth__c} (06 July 1996)
Charity_Referrers__c = {!myVariable_current.Charity_referrers__c} (null)
College_Referrers__c = {!myVariable_current.College_Referrers__c} (null)
County_of_origin__c = {!myVariable_current.County_of_origin__c} (Berkshire)
FirstName = {!myVariable_current.First_Name__c} (Test)
Gender__c = {!myVariable_current.Gender__c} (Female)
LastName = {!myVariable_current.Last_Name__c} (Dodd)
Local_Authority_Referrers__c = {!myVariable_current.Local_Authority_referrers__c} (null)
MobilePhone = {!myVariable_current.Mobile_Phone__c} (06610230804)
Next_of_Kin_First_name__c = {!myVariable_current.Next_of_Kin_First_Name__c} (null)
Next_of_kin_Last_name__c = {!myVariable_current.Next_of_Kin_Last_Name__c} (null)
Previous_accommodation__c = {!myVariable_current.Previous_accommodation__c} (null)
RecordTypeId = 01258000000U464
Referral_Agency__c = {!myVariable_current.Referral_Agency__c} (null)
Social_Services_Referrers__c = {!myVariable_current.Social_Services_Referrers__c} (null)
Town_of_origin__c = {!myVariable_current.Town_of_origin__c} (Slough)
npe01__HomeEmail__c = {!myVariable_current.Email_address__c} (dodd@gmail.com)
Result
Failed to create record.

Error Occurred: INSERT --- INSERT FAILED --- ERRORS : (INVALID_OR_NULL_FOR_RESTRICTED_PICKLIST) bad value for restricted picklist field: Berkshire,