The conversation from 2017 at the bottom might shed some light on the option given to the BTTF investors in September and October of 2016. I believe, at this point, most everyone will elect the swap option (105 SNT for each BTTF share purchased).
It’s not really as simple as that, though. The following recap is based on my personal documentation of this offering back in 2016:
In addition to the actual shares purchased in 2016 a bonus of 2000 coins was to be credited for each investment of 2000 pounds made by, I believe, 9/15/2016. So if you invested 2000 pounds ($2654 USD at the time) you would have purchased 94 shares of the BTTF SPV which amounted to 9870 SNT (105 x 94) and been credited with an additional 2000 coins from the early incentive bonus for a total of 11870 SNT. The following month a bonus was given again for 2000 pounds invested but this time the bonus was only an extra 250 coins for each 2000 pounds if the investment was made by, I believe, 10/15/2016. So in this round your 2000 pounds ($2654 USD) would have netted you 10120 SNT (9870 + 250).
All total, that 4000 pounds (USD$5308) would have bought 188 shares of the SPV and entitled you to a total of 21990 SNT if, in the future, you opted for the coins-for-shares choice. The 21990 coins for 4000 pounds translated, then, to roughly .182 pounds ($.24 USD) per coin, about half what they are trading for today.