What exactly is producing the 65 Mbps figure? No real reason an Ethernet should be slower than 93 Mbps unless its a very very poor Ethernet implementation on the device (93 Mbps being the rough limit for throughput from a 100 Mbps Ethernet port)
The reason for asking is that speed tests depending on how they handle burst speeds can give higher results with wireless occasionally, particularly if it is bursty in nature.
Ethernet will be immune to the problems that can cause wireless issues so should be a lot less buffering normally, and iPlayer has a maximum throughput of around 5 to 6 Mbps even in HD mode so if seeing buffering on any connection above 10 Mbps then you have other issues going in. The 5GHz band is generally a lot better speed wise, but its performance has a sharper cliff due to the attenuation of building materials.