Yes, you can ask to have you line "Re-routed" but charges maybe incurred.. This was something which I looked into prior to my cabinet going FTTC live. At the time the closest (live) FTTC cabinet was situated at the end of the next street away from where I live but the cab I was actually connecting from had not yet been FTTC activated and no information was provided (at the time) if this cab was ever going to be FTTC enabled..
Anyway, a quick email off to NGA asking if I could have my line switched over to the other Live
FTTC who were happy to put me in touch with the relevant BTO dept. which by the time I got a reply it turned out my cabinet which I was already on had became FTTC live.
Also a point on your speed estimates,
From my particular experience I was estimated as 38Mbps down and 6Mbps up which was massive under estimate
. I can actually achieve 68/18.5Mbps [80/20 Profile] which isn't too bad at all considering the initial estimate I had.
I also have a feeling my line can handle much more !