No traffic shaping sounds good.
My current Plusnet 20GB limit service starts shaping during peak hours 4pm - 12am. I reached 13GB during peak so the 1st action level was in place, then reached 17GB and the 2nd action level was reached and they reduced my speed during peak to 128k from 4Mb - lovely

unlimited at all other times though.
My dad had lots of problems migrating from Plusnet to Sky (took 3 months) with each blaming the other. I also like to have control over my router. Is it possible to use my own Netgear router rather than the one Sky issues? It's just I've set up firewall rules for port forwarding and don't fancy having to redo it all.