Is it?
There are many religions being followed in the UK - Christianity, Islam, Hinduism being the three with the largest following. There is a decline in church attendance is some Christian denominations - Cof E and RC in particular, but an increase in others such as the house church movements. Other religions are seeing a rise in attendance in places of worship.
In addition, going to a place of worship is not the only indication of being religious. Many people are religious, believe in the teachings of a religion, but do not belong to the faith in an organised way. they follow their path in an individual way, at home.
I would say that many in the UK are religious, but in a different way. I will be interested to see what happens when the current crisis is over, or at least as near to over that will allow for religious gatherings. Will people be searching for that sense of community or reassurrence and will attendance in places of worship rise? Or will people realise they managed without during lockdown, and not return?
I think people who dismiss religion as superstitious nonsense and say it has not place in the modern world, or that religion is dying are overstating their case. Religiousness is very hard to define. For some people religion is something they turn to in their most desperate need. For some it is not something they wear on their sleeve.
Religious beliefs and teachings have shaped our history, culture, architecture, art, ethics, politics and so much more - sometimes for good, sometimes or bad. Religion, in my opinion, does and will continue to, be an important part of British life.