on your contract, that you signed when you took out the hp will be an amount, after which they cannot take the goods unless you they get a court order. Make a nominal payment, your circumstances may change.
Write aletter of complaint to the people phoning, that is harassment, note the time and dates of the calls, just in case you do go to court, make your offer in writing.
I suspect they have no right to remove the items, if you've nearly paid. don't give up the goods, you will end up with a bigger debt than when you started, they'll add charges, interest all sorts on