Just before I signed up with Virgin Cable Broadband a few months back, I got myself the TP-Link TL-WDR-4300 dual band router.
I experimented with a few different ways of connecting it to the SH, including putting it in modem mode but in the end I found, at least with the TP-Link router, that I didn't have to do much at all.... just turn off the wireless facility in the SH and connect a LAN cable to the WAN port on the router.... works a treat
The WDR-4300 even changed it's default gateway IP address so it didn't conflict with the SH and it means I have the usual LAN ports on the SH available to connect to my Sky Box and I have to say that I've been very impressed with the TP-Link's wireless capabilities and overall performance and given it's very reasonable price, considering it's a DUAL band bit of kit, I'd highly recommend it.