So, having heard from others how a bass shaker can add to VR immersion I decided to have a go a this DIY solution as a project to keep myself busy whilst I wait for my new headset.
I followed this video (not my work) pretty closely, using the subwoofer from a set of 2.1 PC speakers.
https://m.youtube.com/watch?v=m1GS0uIFVfE
I am amazed at how well it works even in this primitive state, worth having a go if you have time and the components to hand!