Collis was a great writer, though at the time several publishers readers thought that he had no writing style.

Where are they now?
His auto biography 'Bound Upon a Course', is a great read too. Also the book that Richard Ingrams wrote just after his death, in a gentle way it puts to bed several myths and self delusions that Collis perpetuated about himself.
As do we all?
If you liked 'Whilst Following the Plough', I would think that you would also enjoy R M Lockley's' Inland Farm'. Lockley was a Welsh ornothologist and early conservationist, who took to mainstream farming during WWII after he was forced to evacuate the island of Skokholm for the duration. He had started living a self-sufficient life there as far back as 1927.
Also his, 'The Island Farmers', about a workers farming co-op that he started , again during the 2nd world war after becoming disillusioned with paying labour wages. His plan was for all to live together and farm collectively. At the time Russia had become a vital ally in the fight against Hitler, and collective farming was thought to be something that would work in Britain by many idealists at the time. This book is fascinating from many viewpoints, as much about cooperation and human nature as anything else, plus there is a lot of farming in it too.
You should find them at Abebooks or Amazon.