If I buy a souvenir plot, do I actually own it?
Purchasers of souvenir plots own a personal right to the plot of land in question, provided that it has been uniquely identified.
Ultimately, this means the vendor cannot legally sell the same plot of land to someone else, but the form of ownership obtained by the purchaser is not recorded in the Land Registry.
It is not in doubt that someone who buys a souvenir plot of land in Scotland obtains some form of ownership over the land in question.
Example 1
If you were to visit the Registers of Scotland and ask them to register Edinburgh Castle in your name, they would most likely say "Sorry Sir, we cannot do that because you don't own it."
Example 2
The DVLA maintain a register of vehicle ownership in the UK.
Bob buys a second-hand car from John. Bob gives John the money and receives the car keys in return.
The next day, before the DVLA has been notified of the transfer of ownership, John regrets the sale, goes to Bob's house and uses the spare keys to enter the vehicle and drives around the countryside.
In this case, John would be guilty of theft because ownership of the car had been transferred to Bob, even though the official registry of car ownership (the DVLA) had no record of the sale.
Conclusion
In a practical sense, whilst the sale of the plot is not recorded in the official public register, the sale has still occurred.
Can an owner of a souvenir plot call himself/herself a Laird, Lord or Lady?
Subject to good faith, there is nothing whatsoever to stop anyone from calling himself/herself a Laird, Lord or Lady.
Some vendors of souvenir plots own intellectual property which they permit customers to use. For example, if you purchase a souvenir plot from www.highlandtitles.com, they will invite you to make use of their registered trademarks Laird of Glencoe™, Lord of Glencoe™ and Lady of Glencoe™.
This question is essentially a marketing question, and most certainly not a question for Lord Lyon who is only concerned with the use of Arms.
Why did the Act in 2012 change the "or" to "and"?
Previously, a souvenir plot was defined as a plot of inconsiderable size or utility.
The Land Registration etc (Scotland) Act 2012 section 22(1)(b) improved upon the definition by replacing the or with and.
Why? It is not difficult to imagine an inconsiderably small plot of land which nonetheless has great value and utility. Such 'ransom strips' are quite common and could potentially prohibit access to property