I think these rulings will vary according to the owner you are dealing with. Most cemeteries are owned by local councils but some are privately owned and some are owned by religious organisations.
This practice is only an issue where land is valuable and / or the cemetery is full to capacity.
I think you will get your information best by phoning and speaking directly to the organisation concerned. Failing that, undertakers in the local area will have a good idea of this, but may be reluctant to help you if you are not 'doing business' with them.