Regarding PN rate Limits / Traffic management policy's you may wish to check out:
Plusnet Traffic Management Support Page
The following is an extract from the above Plusnet URL
Rate Limits
Please note: rate limits are not applied to our current Plusnet Unlimited or Plusnet Business products.
We use rate limits with Plusnet Essentials and some of our older broadband products to make sure everyone gets a good online experience.
IMHO, The only qualm I have with the whole Fibre (FTTx) debate is that regardless whether your ISP of choose limits/throttles your connection/service you are reliant on their traffic management platform which to my knowledge uses Deep-Packet inspection techniques and SPI which in turn de-prioritises your traffic in accordance
THEIR QOS policy.
If using P2P networks be it Bittorrent/FTP/Usenet/IRC.. your maximum throughput could be reduced if you are a heavy user (dependent on several factors).
Also the time it takes for your line to "ramp-up" to its "rated" maximum throughput takes quite a long time, as I have noticed when using some file-sharing services. This could be issues with my network settings MTU/MTS, CTCP, settings etc.. However I doubt it.
One good thing about PN is their level of Support and no-fuss way of sorting things out. which is one of the main reasons I decided to go with them; and of course their product speeds and lack of
obvious rate limits !