They need fire and sun. (And maybe also cold winters). Britain does not have that.
Again the myth of Prometheus, "they need fire, burn, burn, burn"... Yawn.
may die --On California-- UK is a little more humid.
Sequoiadendron grows happy in most temperate areas, including most of Spain. Segovia has some of the tallest trees out of USA, and is a hot place on summer. We have also a few small Sequioadendron forests on the North of Spain since 1950 or even in Granada since 1870. Some Sequioa sempervirens live even in Jaen
(and they don't need fire at all, because gardeners do all the work of taking care for the saplings).
We can plant any tree that we need, were we need it. And we, for sure, will need a lot in the near future.
After all, we put any road that we need where we need it. It was not an obstacle for the last 200 years, so all is needed is the political will to do the same with forests.
The sooner 8 trillion people start planting 3 trillion trees, the better. My quote is filled. Your turn.
The places these trees grow naturally are not naturally fire prone. Go look at any lightning strike map.