https://www.pewresearch.org/religion/2017/11/29/europes-grow...
The most recent birth rate stats I can find is 2005-2010 where Muslims have a birth rate of 3.0 while the rest of the country is at 1.8. Estimates say it's more like 2.5 now, but the current overall UK birth rate is only 1.57 from a quick Google.
https://assets.pewresearch.org/wp-content/uploads/sites/11/2...
The same article also states that the average age for Muslims is much lower than non-Muslims as of 2016, 28 vs 41 for the UK.
https://www.pewresearch.org/wp-content/uploads/sites/7/2017/...
Maybe not in one generation, but in 2-3 generations, the UK will definitely turn Islamic, especially given the exodus of other communities. The irony is that the well-off British are settling in the UAE en masse, a distinctly Islamic country, and driving property prices up there. It's not that much of a concern since local housing is distinctly separated from expat housing.
I don't have a horse in this game - I'm Muslim after all. But I've experienced London pre-immigration boom and post-immigration boom and I definitely prefer the former, like some of my Muslim peers. The fabric of London has already been destroyed, especially when given the fact that London natives have been priced out of their own homes. Given what I've seen firsthand, and what's preached in the mosques of the UK by unleashed and unhinged Imams, the UK is on track to become a Muslim country in 2 or 3 generations.