The use of HVO fuel first cropped up in another thread about buses in the Netherlands.
Today Chiltern Railways have started running locomotives powered by HVO between London and Birmingham.
This is on their Class 68 loco hauled trains, not (yet) on their main DMU fleet. But those trains account for about 1/4 of the daily passenger journeys on Chiltern.
The aim in the UK is to phase out diesel trains by the year 2040, so it is one step towards that goal, as it will never be economically possible to electrify every railway in the UK.