I stayed at Claire's cottage in Cass Bay for 3 nights during a work trip to Christchurch. The daily drive from and to Sydenham was quick and easy, you'd def. would want to have a car though if you're staying in this area of the Christchurch region.

The cottage itself is pretty much brand-new, very well and nicely furnished and an excellent place to stay --- probably even more so if you're on a vacation to enjoy the outdoors in Cass Bay and Port Hills. I didn't really miss anything there, the kitchenette is functional and well stocked and one can even do their laundry and use the dryer in the cottage (I didn't use the laundry though at all).

Be aware that Cass Bay has a limited mobile reception - Vodafone 3G is pretty much only available outdoors, but the cottage has a good and reasonably fast Wifi.