Relocation Expenses

Employer has reimbursed 8K for relocation expenses of employee however employee has incurred about 11K in relocating and all of the costs fall in definition of qualifying relocation expenses. Can we claim any relief for additional expenses or is this 8K is just exemption.

Second thing is a part of that relocation expense claim - reimbursed by employer is travelling costs which employer has reimbursed at 23 pence per mile. Can we claim 17 pence per mile while completing self-assessment on total miles?