Thanks for the feedback Jason.
After some tests, even with fibre broadband, uploading a 8mb file is slow, so the hosting server seems to be the bottleneck, (though no timeout issues as yet)
I think the main issue could be their current choice of host. Hosts who advertise unlimited bandwidth and unlimited space are relying on most clients to have little traffic, I think I just need them to be realistic as to their true resource requirements and budget accordingly ?