It’s always best to use the official Separett pipework where possible because you are assured of a perfect fit and long-term performance. However, there may be situations where this isn’t possible, such as getting the vent pipe around awkward objects or reducing the number of ninety-degree bends.
Flexible pipe (commonly sold as dust extraction pipework) is available in 50mm (for the Tiny) and 75mm (for the Villa) diameters. Try to keep the overall length as short as possible as the flexible pipes often has reinforcing rings which may cause some turbulence and lower the air flow efficiency.