"The righteous were more damaged by their righteousness than the sinners were by their sin"" - John Ortberg.
I think the above sums up legalistic works and rule driven Christianity. JWs fall into this group. Their message is that our denomination is better than your denomination, in fact membership of our church is essential for salvation.
The good new is that there are plenty of grace centred churches out there offering authentic Christian teaching, support and community but without the judgmentalism.
Hillsong is a great church, as is Holy Trinity Brompton in Central London.No doubt there are many near you if you go and explore. Suppress the divisive and unfounded thought that only one church has the "truth". Go where you feel comfortable, ultimately Christianity is about a relationship with God, not membership of any particular church.