This book came out 10 years ago, and I picked it up at a cheap price a few years back. Still available, and there are some very, very cheap copies on Amazon. It's essentially snippet recollections by numerous people. Tony Benn says in the foreward "a must for anyone who really wants to understand Socialism in Britain...it's roots, it's members, it's activities..." There is a section on Co-operation and this is the sort of text you'll find.
"When I came back from the Forces in 1947 I joined both the Labour Party and the Co-operative Party. The Labour Party was by the more exciting of the two. That's not to say it was a thrill a minute, but it was certainly a livelier organisation than the local branch of the Co-operative Party" - Tom Carbery, Glasgow
"I feel the Co-op has been very badly treated by the Labour movement. I don't think their contribution has been quite recognised as it might be. They're always at the tail end of everything, the Co-op. If there's speakers it's unions, and then the Labour Party and then at the tail end." - Isa Paton, Glasgow
There are also some memories of the Labour Party in Withington circa 1938 from people who were young and active at that time.