Hello!
Although there might be other ways, but, since you are interested in buying a router:
- From the above the Netgear DG834 v4 certainly seems interesting given that third party/custom firmware support exists (dgteam, openwrt even tomato by some accounts ... though older versions and likely without modem support ... would have to use the ptcl one as modem in bridge mode) ... if you are comfortable around flashing the firmware, this could allow you to get what you want!
- Also from above, if the Sky/Sagem one is the 2504n model, then it has a great chipset and once unlocked it is very easy to configure as ptcl also uses routers by Sagem though different models ... see here for details:
My Tech Adventures: Sky Sagem 2504n ADSL Wireless Router: Unlock and Info ... might not support bandwidth limits without installing openwrt but it is really a very good modem!
- I would suggest noting down model numbers of routers supporting Tomato or Gargoyle firmware and see if you can find them from the shop (these routers are from 'uk lot stuff' and likely 'sorted' beforehand ... but you might just get lucky)
Regards,
Ahmed