Bunny was a Baptist and a Calvinist. He was saved when some godly women rebuked him for his foul language, he went along to their church and after a great deal of inner struggle and heart wrestling was saved.
Although a simple travelling tinker and so poorly educated, he became a preacher, it was against the law for any to preach without a licence or to hold conventicles with more than 3 people attending. He was thrown into Bedford jail although given the opportunity to submit to the law and be free. He remained in prison for 12 years [17th century jails were awful places] from thence he wrote Pilgrims progress which is second only to the holy bible as most read. It has been translated into every language.
"When walking through the wilderness of this world I did light upon a den..." was Bedford jail.
He is a champion of liberty of speech, freedom of worship...of COURSE he is English.
In the passage he wrote which you quoted Bunyan means christians who all their lives were church goers but never saved, earlier in the book he had described two fellows who had not come in at the narrow gate via the gate-keeper [Christ] but had climbed over the wall into the pilgrim way...these are the same, in the church, people think they are christians, they themselves think they are christians but they have never been born again.
When they come to die , the gateway to heaven, their error becomes apparent.