Probably no help in your case - they don't come into play if you have shares you just want to sell.
They are issued when a company is taken over - ie you have to either sell or lose your shares. Rather than take cash for them there is sometimes (not always) the option of a loan note. Effectively you lend the sale proceeds back to the company and receive them over several years, thus being able to use multiple CGT allowances.
The company doing the takeover has the advantage of not having to pay everything up front and you have the advantage of less (or no) CGT.