I realise that as the service is free, the speed is capped (if I recall correctly at 2Mbits/s). My question is, does the paid service offer an unmetered 100/100+ line?

All I really need for my small, private forum is rock solid speed. By that I mean instant loading.

The paid service does, indeed, offer you a higher speed. But, you "only" get 5MBit/s.