i am genuinely curious why you think attending church reguarly is a requirement for being Christan.
It may not be but it's kinda hard to get figures which separate non-churchgoing Christians and "cultural" Christians. We know that ~60% of people identified as Christian at the 2011 census, we know that in 2007 ~26% attended church at least once a year, so the murky boundary between "cultural" Christians and non-churchgoers is somewhere in the 34%. Churchgoing is the best proxy measurement I can think of, and I'd guess the number of non-churchgoing Christians is comparatively small.
I'd guess about 5% "regularly" go to church.
The same report says 15% of the population attend church monthly, or 10% weekly.