Update from me .... I've now found my underlying problem is Raynauld's Syndrome ..... it's closely related to HAVS.
Whether the bike has triggered it or not I don't know, but both my mother and brother suffer the same. I've investigated and discovered it's related to core body temp and on the bike it's quite easy to get cold - if my brain senses my torso is a little cool the blood vessels in my fingers go into spasm and restrict the blood supply, keeping the blood for the important bits! Reduced activity adds to the problem. Also doesn't help that I've lost a couple of stone in the last year and I need to adapt to wearing a little more when it's cold!
It's even been triggered sat at my desk late one evening when the heating in the office had gone off! Keeping my hands warm doesn't actually help - went skiing in Feb and found that as long as my body stays warm and active, it doesn't matter how cold my fingers get.
Result is that if I make sure I wrap up well on the bike - there's no issue. Going a little light on clothing and the tingling starts followed by full numbness - heated grips on full and winter gloves do absolutely nothing!
Stu.