Yes it's one of those issues that doesn't quite work for everyone. Best option would be to set your Speed at modem setting, upload speed as you require, download speed as unlimited.

I must say that's a 'mighty' difference between upload & download speeds. The country where I live is reknown as having the biggest difference between the two.

Thanks for your help! I've set everything up the way you suggested and *touch wood*, all is going well.

Seems I picked a bad day to test my speeds; I thought at the time my upload speed especially was on the slow side.... thankfully it seems to have gone up much higher now and has stayed there; which in turn has made configuration much easier.
Uploads are still not particularly fast, but at least they don't keep going backwards and stopping at 0/KB like they used to.
Though I think perhaps that could be something to do with how many upload slots I've allowed per person and the maximum slots - I'm still not entirely sure quite how many I should be setting it all to....
My downloads though are much quicker.