Mmm, BT are not known as one of the worst line throttlers out there. I am with BT as well and have about an 8MB connection and I have to admit that I wouldn't normally watch HD because my speed can drop a bit and cause the picture to stutter, so I am not sure about a 5.7MB connection.
That being said, a standard iPlayer program should have no problem with your connection. Are there any certain times of the day that you are trying to use it and have problems?
From about a couple of months ago I started to notice it was likely to struggle around 9pm but was usually OK before then. Now I just get no joy at any time - although on the PC it continues to work without problems.
Gut feeling is its an ISP/local network issue - normally if people get a new modem/router or end up switching ISP's the problems disappear. ISP's handle different versions of iPlayer (there are lots!) differently so if you aren't experienceing similar issues with any of the other services, then fingers would point towards BT I think.
I will try connecting my laptop via the cable used for my tv to check local network, if that works OK I should be able to rule out local network I think.
A few questions about iPlayer / ISPs:
How do I tell if BT are limiting my tv iPlayer?
Can I access the tv version of iPlayer from my laptop? (& if so how)
Can you tell me which version of iPlayer that my tv uses, and anything about it that may be useful?
Is it possible to get the tv to use a different version of iPlayer?
I really appreciate your help. I use the tv iPlayer a lot - or at least used to - but in the last month have only managed to get two programs to run, and for both I had to have half a dozen or so attempts. 3 or 4 months ago I had been using it daily for about a year with no problem apart from occasionally having to watch in lower res than HD.
It could still be a router issue if its an older BT router potentially, although its very hard to pinpoint these issues remotely. Your TV uses MHEG version of iPlayer which is built on Red button technology ( basically the same one that Freesat uses), so its not possible to access it on a PC due to the different architecture.
I will say though, I finally convinced my parents to switch from BT to O2 and they ended up paying 30-40% less than before, got a higher internet speed, resolved their networking issues, better hardware and O2's customer service is very highly regarded in Which? magazine - so there is no harm in at least looking around as benefits extend beyond the TV. Alternatively if you use iPlayer alot, it might be worth looking at one of the current Blu-ray players e.g. BDP-S390 as they feature the new version of iPlayer, V3 which is much more visually appealling, offers proper HD iPlayer, unlike the MHEG version which is only a little better than the SD version.