Does anyone know/have experience as to whether ordinary plastic hose ( fuel compatible of course ) is acceptable at IVA as a fuel tank breather hose or does it have to be a pressure resistant dedicated fuel hose as used for fuel lines? TIA.

I have used a mix of pipe but prefer standard low pressure fuel hose

No need to be HP resistant as long as it's fuel safe. It'll need to be marked as such or have paper work to proove should they ask.