The form of Liability that is most widespread, is apportioned liability under the 1936 Tithe Act where liability created by Rent Tithe Charge is apportioned according to each parish's Record of Ascertainments. Every eligible parish has it's own eccentric method of calculation based upon the amount of Rent Tithe charge collected in the parish (national archive info).
There are some examples across the internet about the amount that a plot would be liable for and absolutely the most detailed conversion showing the breakdown of every field is found on the web at Hartland Archives the introduction is shown here. The people at this archive has then converted each plot into contemporary liability assuming £10,000 of damage to the Chancel. Clearly showing for some plots would be liable to £2 per £10,000 and others and I assume fairly large plots £98 per £10,000. There is also the tithe map available to cross reference with. Whether this gives peace of mind to the locals I do not know but it does show that probably this PCC would consider it not cost effective to notify the liability in their parish.
This is an excellent piece of work based on one form of liability in the Parish of Hartland but there may be other types present in the parish such as, merged tithe and land or land in lieu of tithes. Because the apportionment is available on-line as is the map, if these exist they should be easily traced and these may well be worth notifying the liability on a financial basis.
I consider that a good approximate figure to find each plot and to notify the liability is probably at least £45 and then to enforce the liability at a later date the cost for a PCC could be about £15 per land owner but there would be additional expense above this and if plots have been subdivided then the costs would escalate. There would be naturally pastoral and reputation costs which are hard to quantify.