How often do you see it reported in here or on the news?
Unfortunately I don't know of any UK data on it but in the US far right terrorism has been at play in more incidents than Islamic terror, and not far behind in the death stake.
Islamic terror is "great" at "grand events", whereas far right extremism is at a consistent level, adding up the body count slowly to a similar level in the end.
It's again one of the reasons why Trumps inability to individually condemn the far right was seen as such a big issue.
Edit: For the UK we do know that about a third of people on that terror watchlist are far right suspects. There are several people on here however that refuse to acknowledge that they should also be treated the same as the Muslims on the same list. They claim it's because it's off topic in a Islamic terror thread, yet also refuse to answer in a far right thread.
So many come up with grand ideas about how we will solve the terror problem (as shown in this thread usually incarceration/removal without any due process, at its best), but it should only affect the Muslims, no one else...
It's not about the event, it's about what they can link to it. If it fits their "they're different to me" ideologue then they can use it
Same to an extent with the media. There are multiple murderes every day in Europe, but if it's potentially an Islamic terror attack then it's reported. If ya not, then it's not reported. The idea that perhaps the media and politicians are trying to protect them is falicious at best.