but if you are approached, you can decline and make a claim of your own to the Treasury Solicitor.
https://www.gov.uk/unclaimed-estates-bona-vacantia/overviewIs it worth giving them possibly 40% when they may have done very little in the way of tracing research or taken very little time to find you? ie another family member may have told them about you or they have looked at online electoral registers because you haven't opted out or the BT phone book if you aren't ex-directory.
As to the actual process, the heir hunting company will/may have purchased certificates and the costs of those will come out of the estate before distribution. If you are approached, you may be asked to send a copy of your own certificates, this keeps costs down but if you are unwilling or unable to supply copies, they will order them anyway.
If you would like to see any certificates that have been used to compile the tree, contact the personal representive but they may be unwilling to share because of data protection policies. Some people may state that they do not want their details shared or to be contacted by estranged family members.
The GRO are unable to offer discounts as the statutory cost is currently £9.25
Local register offices charge a bit more as they are no longer part of the GRO (£10+), they are employed by local authorities now.
And as lovely as the tree is, the cost of producing however many copies will come out of the estate so you will have paid for it in a roundabout way.