PostDoc relocation Expenses
You have been told (by HR I assume) that postdocs can not claim their relocation expenses from the University. However, there is a chance you can claim (some) reimbursement from the School/Department or from your PI's grant. It is a bit late to negotiate this already, but it probably does not hurt to ask.

However, if the answer appears to be negative, unfortunately, there is not much to be done. Welcome to the dark side of academia.