Aspect 8, which has 25 Financial Planners, including a number of Chartered Financial Planners and PFS Fellows, as well as four Paraplanners, is part of the deal. It was formed in 1993.
The other business is Evolution Wealth, which is a small network and Chartered Financial Planning firm. Both are based in Horsham, Sussex.
The two companies come under the umbrella of Benchmark Capital.
Schroders has taken the stake in Best Practice and parent company Benchmark Capital for an undisclosed fee.
Benchmark also includes platform Fusion Wealth and technology firm Creative Technologies.
Benchmark Capital chief executive Ian Cooke will remain a core owner of the business and will continue as chief executive of Best Practice and Benchmark Capital.
He said: “Our business has grown significantly over the last few years by focusing on integrated technology and professionalism and we have been actively seeking to partner with a company who shares our values and explore new opportunities.
“Partnering with Schroders, a FTSE 100 global investment management company, will provide Benchmark Capital with access to new markets and further enhance our proposition. We will continue to improve our technology suite bringing these benefits to our UK clients. As a core owner, I am excited about our future growth.”
Schroders group chief executive Peter Harrison will join the board of Benchmark Capital as chairman.
The existing executive team will continue to run the business day-to-day.
Mr Harrison said: “This is a significant step in the growth of our presence in the UK retail investment market which is of strategic importance to the group. There is a strong cultural fit between our two businesses, with a shared commitment to delivering investment excellence and high-quality service for clients.”
Schroders intermediary director Robin Stoakley and global head of wealth Andrew Ross will also join as non-executive directors.
Mr Stoakley said: “Benchmark Capital’s affluent and mass affluent expertise is complementary to Schroders’ investment management and high net worth client management expertise.
“This combination will enable us to develop a better understanding of investor behaviours across the retail client spectrum, which will ultimately lead to better client outcomes. This partnership also allows us to offer existing clients the services of a high-quality adviser support business.”
The expected completion date is set for early next year.