Hi and welcome to The-T-Bar.
I remain convinced, as I was when I bought my 135 TF, that the VVC is probably not worth the bother (unless you really want the absolute maximum performance from your MG). They are generally more expensive to buy, cost more to maintain and potentially have more to go wrong. The 135 is plenty quick enough for most legal driving, particularly if you wind up the revs a bit. I suspect that the VVC will only really unleash its fury at very high revs - The red line is at 7,250RPM.
As for the F Steptronic and TF Stepspeed, I have no experience although I know someone who has had one for a few years and it has given him no trouble. There is
an interesting article on this here
.
Good luck in your search