For a leg, I'd butterfly it, marinate it over night then grill it direct, hot and fast! I did it with a goat leg a while back and it was fantastic.
After a few hours it won't take on any more smoke and once it gets to about 60C it'll hit the stall. UK briskets don't generally have the same fat content as US ones either so I'd wrap it to power through the stall and keep more of the juice in. I tend to get the point end of the brisket so it's a bit fattier and a larger piece is always more forgiving as well, plus it means you can have left overs for burnt ends!
I had a cheap supermarket rump I was going to use on a baguette this afternoon so thought I'd fire up the Vortex and see how well it works for searing steaks.