Hi @Ana1976, thanks for your post here in the community - welcome to Virgin Media!
As @Tudor has suggested, we do aim on the day to get everything working and the large majority of the time this is successful.
However, nothing is guaranteed as there can be issues on the day which are unexpected (it's hard to give specific examples), but I really wouldn't worry as we'll do our best to get it working for you on the day!
I hope this helps.
Many thanks
Tom_W