UKC

I'm most likely going to go with BMC but has anyone used a different provider for travel around Svalbard for hiking etc (ie not just visiting Longyearbyen)

Not for Svalbard but just taken out insurance with Snowcard to cover a trip including the Arctic Circle Trail in Greenland (so probably similar to what you need).  I had a query on what level of cover to get and they responded very quickly.  So impressed with their customer service and was cheaper than BMC would have been.

Don't know Snowcard, I usually use BMC byt Snowcard are backed by Ageas, who do a lot of travel insurance in all fields and more importantly are UK on-shore insurer and are backed by FOS. Should be fine

Used to use Dogtag but there's a bit of an issue with them on another thread. I'll be going with Snowcard for our next trip after many recommendations on here.