I am an ACCA member with 2.5 post qualifications experience and 4.5 year pre qualification at Big Four.

I don't have bachelor's degree. I find it difficult to get in to Financial Times ranked Universities in UK.

I have only applied for University of Liverpool, they feel that my academic qualification is less.

Kindly let me know which way to get in to best Business Schools.

Will me doing GMAT help me get into one.

This depends on your goals. I don't think anyone would say that Liverpool was one of the best business schools in the UK. I think it would be wise for you to get a top-up bachelor's degree or to look at options like the University of Birmingham diploma. 

I think it's possible but you might have to ask the schools directly and in general you want to provide alternative evidence that you are able to pursue a rigorous degree.

A GMAT would help, as would any additional academic qualifications that you could provide. (certificates, online classes, etc.)

Look into 'open entry' applications, where schools look into your work experience. 

[Edited by Larry on Aug 28, 2020]