How much do I have to borrow if I turnover £4,000,000?

I run a business services agency providing a consultancy service to large corporate. My projected turnover for the next 12 month is £4,000,000, up from £3,250,000 last year, which was our fifth year trading.

After a few cash flow issues last year my accountant has advised that I use an invoice discounting service, but was super helpful by saying they couldn’t recommend anyone to us.

Does anyone know what to look out for when finding the right provider? Should I just look at the cost and go with the cheapest?

How much does invoice finance cost for manufacturing business?