oh, ok. I misunderstood. Like the good old days when you ordered ISDN
64, because that featured free fibre installation, cancelled it after a month and ordered a 2Mbps link to the ISP over it afterwards :-)used to be £3500 back in the day.
But yes, you need to have a reason for that. But seriously it is in Openreach's interest to go FTTP as fast as it can. Its lower maintenance and higher speeds.
Of course if you want it sooner and have £3500 burning a hole on yer pocket...