Attached a 24TB qnap nas box at home had it filling at full speed all night 3 threads from a 10Gbps box and i was maxed solid for 8 hours last night, 24000KB/s - 24MB/s down, consistently.
Never had any speed issues with virgin in either my wigan flat or leeds home, rock solid it has been for me.
In general if you can get virgin you will get great speeds, the network is very good tbh, even compared to most other countries.
As an ftp siteop i get to see people speeds out and how stable the line is. I would say virgin is hands down the best then bt, then sky big 3 wise.
The best ones have been small isp's in a who cover small geographical areas.
One guy is in a virgin test area and currently has 500Mbps download, fucker. That is 5 x 100Mbps servers, for a uk domestic line that is very impressive.
As a dedicated file sharer there is no comparison, you use virgin broadband, others are not even close tbh.
A good tip for you guys is call them and ask the fup policy is removed if you don't hammer the line. They will remove the peak time data limits placed on you.
Just say you sometimes help with non profit stuff that requires constant high bw due to cloud distrubuted computing, but this is only once every now and then.
I have had mine removed and hammered my downlink for a week now and no peak time data limits/speed limits :-)