If there are no major issues, your mother could arrange to Extract a Grant in the Probate Office. It would be advisable thereafter to instruct a solicitor to draft the necessary paperwork to transfer ownership.
If your father left a will, leaving everything to your mother, it is fairly straightforward. If there was no will, it is more complicated - as the offspring would also have an interest.
Yes, there is a fair amount of work involved. It is not normally charged as a percentage of the property value.
Get your paperwork in order ( details all assets held in joint/sole names) and meet with a local, recommended solicitor for an inital interview - on the basis that they can give you a costs analysis once they see what is involved.
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