Honestly, sign up for ADSL/VDSL once thats in and going contact your ISP and sign up for fibre. it may say 2 weeks but don't count on it.
Dont cancel the VDSL till the fibre is in and working, common mistake having A/VDSL turn off the day fibre is suppose to be installed and it not actually happening and then being left with out a connection.
How does VDSL keep working if fibre is pulled through the underground pipe replacing the copper?
Is there a very short down time while the ONT, etc is installed?