Hi, can anybody confirm if I will need two WAN connections at both ends to achieve VPN trunking..

My plan is at head office to have two wan connections, but at the remote site have one WAN connection but the VPNS fail-over between either of the WAN connections at head office, the reason for this is that my remote sites WAN is solid and never lets me down, but head office is up and down like a yo-yo.

nah you can have a VPN trunk going from two WANs to a single wAN but both routers need to support VPN trunk i.e. 2850 and upwards.
this guide here shows how you can do it:
http://www.draytek.com/index.php?option=com_k2&view=item&id=2021