They are as reliable as you want them to be, ie look after them and there is no problem.
I did 190 miles yesterday in my 170,000+ bottom end cossie sapph, and would not hesitate to do any distance at all in 100% total confidence.
When I first got the car I had of course to fix all the running problems caused by neglect and previous owners who couldn't afford to run the car.
The head gasket blew on way to a meet, but still managed to nurse it home 20 miles with regular topping up, even though water was dribbling from block!!
Mine has never broke down, no reason they should at all.
I have just added a towbar to mine.
It's not unusual to do 1000 miles some weeks, if busy, but others as little as 300.
As to BT or ST, depends if you want to tune, most do as the escos is 4wd the boxes become the weak point over 350bhp, so a stage 3 is ideal, and really nice, will not affect reliability, old age and things wearing out will, 99.9% can be prevented with maintenance, and even that isn't a lot, and they are easy to work on.
tabetha