Last week private equity firm Cinven agreed to become majority shareholder of True Potential for an undisclosed sum.
But Harrison said he also considered offers from large corporates, such as the bank and fund houses, as well as Spacs.
He said: "One of the reasons [we didn't accept their offer] was we felt we would probably be stifled if a larger corporate acquired us at this stage of our growth."
Harrison added: "As always, we have been very open minded about our options. It is important to do that because you can close off opportunities.
"We got to know some very good Spacs both in the United States and in Europe. At the same time we were looking at an IPO.
"We decided to go with the private side of things and the main reason why was we can continue to work in the way we work. That’s not because we have anything to hide - far from it - it is the way we grew up. With public you’ve got to be a bit more methodical.
"Cinven were one of four firms to put in really thrilling offers."
He said part of the appeal of Cinven was they already worked with regulated companies and were familiar with the financial advice sector.
Harrison confirmed the Spac set up by Bernard Arnault, one of the world's richest men and the chief executive of luxury goods company LVMH, was on of the parties True Potential spoke to.
He added: "Cinven typically hold for five years [...] For us it is to get on with hitting the plan and then we will probably lift our heads up in two to three years and see where the business is at. See what’s around.
"It could be public is perfect for True Potential at that stage because we have reached that inflection point."