Some of the places where tea is grown have a cold winter, like Darjeeling, and parts of Japan. Tea is notably grown around Kyoto in Japan, whose mid-winter is as cold as SE England. Many places where tea is grown are frost free, and there are many varieties of C sinensis, which likely have different levels of hardiness.

However all of the places where tea is normally grown have a warm wet season, much wetter and warmer than SE England. So this makes the plant grow much faster than it would in England during the growing season. I expect you'd have to prune it much more gingerly than in Britain. And water it with huge quantities of soft water. Many plants only survive a cold winter if they had a warm summer to ripen them well, which is why we can't grow many plants from arid and mediterranean regions in Britain, even though they have very sharp winter frosts in their native area of growth.

If you look at pictures of tea estates, you will see that the tea bushes look like well-pruned hedges, pretty much like the 3ft laurel hedge I have in my front garden. So that is the kind of pruning you are aiming for. Tea that is made with just the new shoots (May in Darjeeling) is called First Flush, and is a lighter brew, and much more expensive. There is also Second Flush (July-ish). Main crop is autumnal, and that is cheapest and most abundant. I have seen tea picking at the Boh estate in Cameron highlands in Malaysia. The pickers had a pair of shears, with foot blades and similar handles, just like you would prune your hedge with, but it had a "catcher" on it, like a dustpan, which caught the prunings, which the pickers then threw over there shoulders into a basket on their back. Top quality early season tea is picked by hand, selecting leaves individually, and takes an inordinate amount of labour per pack of tea - they pick just the top pair of leaves from each stem when doing this.

Then you have to process the leaves to make it into tea. That's a skilled task too, and quite time critical.